![Herbert Xu](/assets/img/avatar_default.png)
It is legitimate to call tcp_fragment with len == skb->len since that is done for FIN packets and the FIN flag counts as one byte. So we should only check for the len > skb->len case. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
2061 lines
59 KiB
C
2061 lines
59 KiB
C
/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* Implementation of the Transmission Control Protocol(TCP).
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*
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* Version: $Id: tcp_output.c,v 1.146 2002/02/01 22:01:04 davem Exp $
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*
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* Authors: Ross Biro
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* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
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* Mark Evans, <evansmp@uhura.aston.ac.uk>
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* Corey Minyard <wf-rch!minyard@relay.EU.net>
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* Florian La Roche, <flla@stud.uni-sb.de>
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* Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
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* Linus Torvalds, <torvalds@cs.helsinki.fi>
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* Alan Cox, <gw4pts@gw4pts.ampr.org>
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* Matthew Dillon, <dillon@apollo.west.oic.com>
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* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
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* Jorge Cwik, <jorge@laser.satlink.net>
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*/
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/*
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* Changes: Pedro Roque : Retransmit queue handled by TCP.
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* : Fragmentation on mtu decrease
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* : Segment collapse on retransmit
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* : AF independence
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*
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* Linus Torvalds : send_delayed_ack
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* David S. Miller : Charge memory using the right skb
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* during syn/ack processing.
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* David S. Miller : Output engine completely rewritten.
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* Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
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* Cacophonix Gaul : draft-minshall-nagle-01
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* J Hadi Salim : ECN support
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*
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*/
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#include <net/tcp.h>
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#include <linux/compiler.h>
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#include <linux/module.h>
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#include <linux/smp_lock.h>
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/* People can turn this off for buggy TCP's found in printers etc. */
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int sysctl_tcp_retrans_collapse = 1;
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/* This limits the percentage of the congestion window which we
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* will allow a single TSO frame to consume. Building TSO frames
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* which are too large can cause TCP streams to be bursty.
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*/
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int sysctl_tcp_tso_win_divisor = 3;
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static inline void update_send_head(struct sock *sk, struct tcp_sock *tp,
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struct sk_buff *skb)
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{
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sk->sk_send_head = skb->next;
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if (sk->sk_send_head == (struct sk_buff *)&sk->sk_write_queue)
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sk->sk_send_head = NULL;
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tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
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tcp_packets_out_inc(sk, tp, skb);
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}
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/* SND.NXT, if window was not shrunk.
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* If window has been shrunk, what should we make? It is not clear at all.
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* Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
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* Anything in between SND.UNA...SND.UNA+SND.WND also can be already
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* invalid. OK, let's make this for now:
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*/
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static inline __u32 tcp_acceptable_seq(struct sock *sk, struct tcp_sock *tp)
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{
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if (!before(tp->snd_una+tp->snd_wnd, tp->snd_nxt))
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return tp->snd_nxt;
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else
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return tp->snd_una+tp->snd_wnd;
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}
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/* Calculate mss to advertise in SYN segment.
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* RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
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*
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* 1. It is independent of path mtu.
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* 2. Ideally, it is maximal possible segment size i.e. 65535-40.
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* 3. For IPv4 it is reasonable to calculate it from maximal MTU of
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* attached devices, because some buggy hosts are confused by
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* large MSS.
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* 4. We do not make 3, we advertise MSS, calculated from first
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* hop device mtu, but allow to raise it to ip_rt_min_advmss.
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* This may be overridden via information stored in routing table.
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* 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
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* probably even Jumbo".
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*/
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static __u16 tcp_advertise_mss(struct sock *sk)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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struct dst_entry *dst = __sk_dst_get(sk);
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int mss = tp->advmss;
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if (dst && dst_metric(dst, RTAX_ADVMSS) < mss) {
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mss = dst_metric(dst, RTAX_ADVMSS);
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tp->advmss = mss;
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}
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return (__u16)mss;
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}
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/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
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* This is the first part of cwnd validation mechanism. */
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static void tcp_cwnd_restart(struct sock *sk, struct dst_entry *dst)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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s32 delta = tcp_time_stamp - tp->lsndtime;
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u32 restart_cwnd = tcp_init_cwnd(tp, dst);
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u32 cwnd = tp->snd_cwnd;
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tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
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tp->snd_ssthresh = tcp_current_ssthresh(sk);
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restart_cwnd = min(restart_cwnd, cwnd);
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while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
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cwnd >>= 1;
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tp->snd_cwnd = max(cwnd, restart_cwnd);
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tp->snd_cwnd_stamp = tcp_time_stamp;
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tp->snd_cwnd_used = 0;
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}
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static inline void tcp_event_data_sent(struct tcp_sock *tp,
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struct sk_buff *skb, struct sock *sk)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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const u32 now = tcp_time_stamp;
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if (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto)
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tcp_cwnd_restart(sk, __sk_dst_get(sk));
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tp->lsndtime = now;
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/* If it is a reply for ato after last received
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* packet, enter pingpong mode.
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*/
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if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
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icsk->icsk_ack.pingpong = 1;
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}
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static __inline__ void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
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{
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tcp_dec_quickack_mode(sk, pkts);
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inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
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}
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/* Determine a window scaling and initial window to offer.
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* Based on the assumption that the given amount of space
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* will be offered. Store the results in the tp structure.
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* NOTE: for smooth operation initial space offering should
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* be a multiple of mss if possible. We assume here that mss >= 1.
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* This MUST be enforced by all callers.
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*/
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void tcp_select_initial_window(int __space, __u32 mss,
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__u32 *rcv_wnd, __u32 *window_clamp,
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int wscale_ok, __u8 *rcv_wscale)
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{
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unsigned int space = (__space < 0 ? 0 : __space);
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/* If no clamp set the clamp to the max possible scaled window */
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if (*window_clamp == 0)
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(*window_clamp) = (65535 << 14);
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space = min(*window_clamp, space);
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/* Quantize space offering to a multiple of mss if possible. */
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if (space > mss)
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space = (space / mss) * mss;
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/* NOTE: offering an initial window larger than 32767
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* will break some buggy TCP stacks. We try to be nice.
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* If we are not window scaling, then this truncates
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* our initial window offering to 32k. There should also
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* be a sysctl option to stop being nice.
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*/
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(*rcv_wnd) = min(space, MAX_TCP_WINDOW);
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(*rcv_wscale) = 0;
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if (wscale_ok) {
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/* Set window scaling on max possible window
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* See RFC1323 for an explanation of the limit to 14
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*/
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space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
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while (space > 65535 && (*rcv_wscale) < 14) {
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space >>= 1;
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(*rcv_wscale)++;
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}
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}
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/* Set initial window to value enough for senders,
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* following RFC2414. Senders, not following this RFC,
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* will be satisfied with 2.
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*/
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if (mss > (1<<*rcv_wscale)) {
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int init_cwnd = 4;
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if (mss > 1460*3)
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init_cwnd = 2;
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else if (mss > 1460)
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init_cwnd = 3;
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if (*rcv_wnd > init_cwnd*mss)
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*rcv_wnd = init_cwnd*mss;
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}
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/* Set the clamp no higher than max representable value */
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(*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
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}
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/* Chose a new window to advertise, update state in tcp_sock for the
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* socket, and return result with RFC1323 scaling applied. The return
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* value can be stuffed directly into th->window for an outgoing
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* frame.
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*/
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static __inline__ u16 tcp_select_window(struct sock *sk)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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u32 cur_win = tcp_receive_window(tp);
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u32 new_win = __tcp_select_window(sk);
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/* Never shrink the offered window */
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if(new_win < cur_win) {
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/* Danger Will Robinson!
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* Don't update rcv_wup/rcv_wnd here or else
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* we will not be able to advertise a zero
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* window in time. --DaveM
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*
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* Relax Will Robinson.
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*/
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new_win = cur_win;
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}
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tp->rcv_wnd = new_win;
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tp->rcv_wup = tp->rcv_nxt;
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/* Make sure we do not exceed the maximum possible
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* scaled window.
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*/
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if (!tp->rx_opt.rcv_wscale)
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new_win = min(new_win, MAX_TCP_WINDOW);
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else
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new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
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/* RFC1323 scaling applied */
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new_win >>= tp->rx_opt.rcv_wscale;
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/* If we advertise zero window, disable fast path. */
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if (new_win == 0)
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tp->pred_flags = 0;
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return new_win;
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}
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/* This routine actually transmits TCP packets queued in by
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* tcp_do_sendmsg(). This is used by both the initial
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* transmission and possible later retransmissions.
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* All SKB's seen here are completely headerless. It is our
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* job to build the TCP header, and pass the packet down to
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* IP so it can do the same plus pass the packet off to the
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* device.
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*
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* We are working here with either a clone of the original
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* SKB, or a fresh unique copy made by the retransmit engine.
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*/
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static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb)
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{
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if (skb != NULL) {
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const struct inet_connection_sock *icsk = inet_csk(sk);
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struct inet_sock *inet = inet_sk(sk);
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struct tcp_sock *tp = tcp_sk(sk);
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struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
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int tcp_header_size = tp->tcp_header_len;
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struct tcphdr *th;
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int sysctl_flags;
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int err;
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BUG_ON(!tcp_skb_pcount(skb));
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#define SYSCTL_FLAG_TSTAMPS 0x1
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#define SYSCTL_FLAG_WSCALE 0x2
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#define SYSCTL_FLAG_SACK 0x4
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/* If congestion control is doing timestamping */
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if (icsk->icsk_ca_ops->rtt_sample)
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__net_timestamp(skb);
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sysctl_flags = 0;
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if (tcb->flags & TCPCB_FLAG_SYN) {
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tcp_header_size = sizeof(struct tcphdr) + TCPOLEN_MSS;
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if(sysctl_tcp_timestamps) {
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tcp_header_size += TCPOLEN_TSTAMP_ALIGNED;
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sysctl_flags |= SYSCTL_FLAG_TSTAMPS;
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}
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if(sysctl_tcp_window_scaling) {
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tcp_header_size += TCPOLEN_WSCALE_ALIGNED;
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sysctl_flags |= SYSCTL_FLAG_WSCALE;
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}
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if(sysctl_tcp_sack) {
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sysctl_flags |= SYSCTL_FLAG_SACK;
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if(!(sysctl_flags & SYSCTL_FLAG_TSTAMPS))
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tcp_header_size += TCPOLEN_SACKPERM_ALIGNED;
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}
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} else if (tp->rx_opt.eff_sacks) {
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/* A SACK is 2 pad bytes, a 2 byte header, plus
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* 2 32-bit sequence numbers for each SACK block.
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*/
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tcp_header_size += (TCPOLEN_SACK_BASE_ALIGNED +
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(tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK));
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}
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if (tcp_packets_in_flight(tp) == 0)
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tcp_ca_event(sk, CA_EVENT_TX_START);
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th = (struct tcphdr *) skb_push(skb, tcp_header_size);
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skb->h.th = th;
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skb_set_owner_w(skb, sk);
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/* Build TCP header and checksum it. */
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th->source = inet->sport;
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th->dest = inet->dport;
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th->seq = htonl(tcb->seq);
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th->ack_seq = htonl(tp->rcv_nxt);
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*(((__u16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) | tcb->flags);
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if (tcb->flags & TCPCB_FLAG_SYN) {
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/* RFC1323: The window in SYN & SYN/ACK segments
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* is never scaled.
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*/
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th->window = htons(tp->rcv_wnd);
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} else {
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th->window = htons(tcp_select_window(sk));
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}
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th->check = 0;
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th->urg_ptr = 0;
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if (tp->urg_mode &&
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between(tp->snd_up, tcb->seq+1, tcb->seq+0xFFFF)) {
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th->urg_ptr = htons(tp->snd_up-tcb->seq);
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th->urg = 1;
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}
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if (tcb->flags & TCPCB_FLAG_SYN) {
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tcp_syn_build_options((__u32 *)(th + 1),
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tcp_advertise_mss(sk),
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(sysctl_flags & SYSCTL_FLAG_TSTAMPS),
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(sysctl_flags & SYSCTL_FLAG_SACK),
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(sysctl_flags & SYSCTL_FLAG_WSCALE),
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tp->rx_opt.rcv_wscale,
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tcb->when,
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tp->rx_opt.ts_recent);
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} else {
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tcp_build_and_update_options((__u32 *)(th + 1),
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tp, tcb->when);
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TCP_ECN_send(sk, tp, skb, tcp_header_size);
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}
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tp->af_specific->send_check(sk, th, skb->len, skb);
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if (tcb->flags & TCPCB_FLAG_ACK)
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tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
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if (skb->len != tcp_header_size)
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tcp_event_data_sent(tp, skb, sk);
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TCP_INC_STATS(TCP_MIB_OUTSEGS);
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err = tp->af_specific->queue_xmit(skb, 0);
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if (err <= 0)
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return err;
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tcp_enter_cwr(sk);
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/* NET_XMIT_CN is special. It does not guarantee,
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* that this packet is lost. It tells that device
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* is about to start to drop packets or already
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* drops some packets of the same priority and
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* invokes us to send less aggressively.
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*/
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return err == NET_XMIT_CN ? 0 : err;
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}
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return -ENOBUFS;
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#undef SYSCTL_FLAG_TSTAMPS
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#undef SYSCTL_FLAG_WSCALE
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#undef SYSCTL_FLAG_SACK
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}
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/* This routine just queue's the buffer
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*
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* NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
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* otherwise socket can stall.
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*/
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static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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/* Advance write_seq and place onto the write_queue. */
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tp->write_seq = TCP_SKB_CB(skb)->end_seq;
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skb_header_release(skb);
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__skb_queue_tail(&sk->sk_write_queue, skb);
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sk_charge_skb(sk, skb);
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/* Queue it, remembering where we must start sending. */
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if (sk->sk_send_head == NULL)
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sk->sk_send_head = skb;
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}
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static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
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{
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if (skb->len <= mss_now ||
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!(sk->sk_route_caps & NETIF_F_TSO)) {
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/* Avoid the costly divide in the normal
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* non-TSO case.
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*/
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skb_shinfo(skb)->tso_segs = 1;
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skb_shinfo(skb)->tso_size = 0;
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} else {
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unsigned int factor;
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factor = skb->len + (mss_now - 1);
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factor /= mss_now;
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skb_shinfo(skb)->tso_segs = factor;
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skb_shinfo(skb)->tso_size = mss_now;
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}
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}
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/* Function to create two new TCP segments. Shrinks the given segment
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* to the specified size and appends a new segment with the rest of the
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* packet to the list. This won't be called frequently, I hope.
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* Remember, these are still headerless SKBs at this point.
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*/
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int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss_now)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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struct sk_buff *buff;
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int nsize, old_factor;
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u16 flags;
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BUG_ON(len > skb->len);
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nsize = skb_headlen(skb) - len;
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if (nsize < 0)
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nsize = 0;
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if (skb_cloned(skb) &&
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skb_is_nonlinear(skb) &&
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pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
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return -ENOMEM;
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/* Get a new skb... force flag on. */
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buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC);
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if (buff == NULL)
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return -ENOMEM; /* We'll just try again later. */
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sk_charge_skb(sk, buff);
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|
|
|
/* Correct the sequence numbers. */
|
|
TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
|
|
TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
|
|
TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
|
|
|
|
/* PSH and FIN should only be set in the second packet. */
|
|
flags = TCP_SKB_CB(skb)->flags;
|
|
TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
|
|
TCP_SKB_CB(buff)->flags = flags;
|
|
TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_AT_TAIL;
|
|
|
|
if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_HW) {
|
|
/* Copy and checksum data tail into the new buffer. */
|
|
buff->csum = csum_partial_copy_nocheck(skb->data + len, skb_put(buff, nsize),
|
|
nsize, 0);
|
|
|
|
skb_trim(skb, len);
|
|
|
|
skb->csum = csum_block_sub(skb->csum, buff->csum, len);
|
|
} else {
|
|
skb->ip_summed = CHECKSUM_HW;
|
|
skb_split(skb, buff, len);
|
|
}
|
|
|
|
buff->ip_summed = skb->ip_summed;
|
|
|
|
/* Looks stupid, but our code really uses when of
|
|
* skbs, which it never sent before. --ANK
|
|
*/
|
|
TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
|
|
buff->tstamp = skb->tstamp;
|
|
|
|
old_factor = tcp_skb_pcount(skb);
|
|
|
|
/* Fix up tso_factor for both original and new SKB. */
|
|
tcp_set_skb_tso_segs(sk, skb, mss_now);
|
|
tcp_set_skb_tso_segs(sk, buff, mss_now);
|
|
|
|
/* If this packet has been sent out already, we must
|
|
* adjust the various packet counters.
|
|
*/
|
|
if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
|
|
int diff = old_factor - tcp_skb_pcount(skb) -
|
|
tcp_skb_pcount(buff);
|
|
|
|
tp->packets_out -= diff;
|
|
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
|
|
tp->sacked_out -= diff;
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
|
|
tp->retrans_out -= diff;
|
|
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
|
|
tp->lost_out -= diff;
|
|
tp->left_out -= diff;
|
|
}
|
|
|
|
if (diff > 0) {
|
|
/* Adjust Reno SACK estimate. */
|
|
if (!tp->rx_opt.sack_ok) {
|
|
tp->sacked_out -= diff;
|
|
if ((int)tp->sacked_out < 0)
|
|
tp->sacked_out = 0;
|
|
tcp_sync_left_out(tp);
|
|
}
|
|
|
|
tp->fackets_out -= diff;
|
|
if ((int)tp->fackets_out < 0)
|
|
tp->fackets_out = 0;
|
|
}
|
|
}
|
|
|
|
/* Link BUFF into the send queue. */
|
|
skb_header_release(buff);
|
|
__skb_append(skb, buff, &sk->sk_write_queue);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
|
|
* eventually). The difference is that pulled data not copied, but
|
|
* immediately discarded.
|
|
*/
|
|
static unsigned char *__pskb_trim_head(struct sk_buff *skb, int len)
|
|
{
|
|
int i, k, eat;
|
|
|
|
eat = len;
|
|
k = 0;
|
|
for (i=0; i<skb_shinfo(skb)->nr_frags; i++) {
|
|
if (skb_shinfo(skb)->frags[i].size <= eat) {
|
|
put_page(skb_shinfo(skb)->frags[i].page);
|
|
eat -= skb_shinfo(skb)->frags[i].size;
|
|
} else {
|
|
skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
|
|
if (eat) {
|
|
skb_shinfo(skb)->frags[k].page_offset += eat;
|
|
skb_shinfo(skb)->frags[k].size -= eat;
|
|
eat = 0;
|
|
}
|
|
k++;
|
|
}
|
|
}
|
|
skb_shinfo(skb)->nr_frags = k;
|
|
|
|
skb->tail = skb->data;
|
|
skb->data_len -= len;
|
|
skb->len = skb->data_len;
|
|
return skb->tail;
|
|
}
|
|
|
|
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
|
|
{
|
|
if (skb_cloned(skb) &&
|
|
pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
|
|
return -ENOMEM;
|
|
|
|
if (len <= skb_headlen(skb)) {
|
|
__skb_pull(skb, len);
|
|
} else {
|
|
if (__pskb_trim_head(skb, len-skb_headlen(skb)) == NULL)
|
|
return -ENOMEM;
|
|
}
|
|
|
|
TCP_SKB_CB(skb)->seq += len;
|
|
skb->ip_summed = CHECKSUM_HW;
|
|
|
|
skb->truesize -= len;
|
|
sk->sk_wmem_queued -= len;
|
|
sk->sk_forward_alloc += len;
|
|
sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
|
|
|
|
/* Any change of skb->len requires recalculation of tso
|
|
* factor and mss.
|
|
*/
|
|
if (tcp_skb_pcount(skb) > 1)
|
|
tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk, 1));
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* This function synchronize snd mss to current pmtu/exthdr set.
|
|
|
|
tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
|
|
for TCP options, but includes only bare TCP header.
|
|
|
|
tp->rx_opt.mss_clamp is mss negotiated at connection setup.
|
|
It is minumum of user_mss and mss received with SYN.
|
|
It also does not include TCP options.
|
|
|
|
tp->pmtu_cookie is last pmtu, seen by this function.
|
|
|
|
tp->mss_cache is current effective sending mss, including
|
|
all tcp options except for SACKs. It is evaluated,
|
|
taking into account current pmtu, but never exceeds
|
|
tp->rx_opt.mss_clamp.
|
|
|
|
NOTE1. rfc1122 clearly states that advertised MSS
|
|
DOES NOT include either tcp or ip options.
|
|
|
|
NOTE2. tp->pmtu_cookie and tp->mss_cache are READ ONLY outside
|
|
this function. --ANK (980731)
|
|
*/
|
|
|
|
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int mss_now;
|
|
|
|
/* Calculate base mss without TCP options:
|
|
It is MMS_S - sizeof(tcphdr) of rfc1122
|
|
*/
|
|
mss_now = pmtu - tp->af_specific->net_header_len - sizeof(struct tcphdr);
|
|
|
|
/* Clamp it (mss_clamp does not include tcp options) */
|
|
if (mss_now > tp->rx_opt.mss_clamp)
|
|
mss_now = tp->rx_opt.mss_clamp;
|
|
|
|
/* Now subtract optional transport overhead */
|
|
mss_now -= tp->ext_header_len;
|
|
|
|
/* Then reserve room for full set of TCP options and 8 bytes of data */
|
|
if (mss_now < 48)
|
|
mss_now = 48;
|
|
|
|
/* Now subtract TCP options size, not including SACKs */
|
|
mss_now -= tp->tcp_header_len - sizeof(struct tcphdr);
|
|
|
|
/* Bound mss with half of window */
|
|
if (tp->max_window && mss_now > (tp->max_window>>1))
|
|
mss_now = max((tp->max_window>>1), 68U - tp->tcp_header_len);
|
|
|
|
/* And store cached results */
|
|
tp->pmtu_cookie = pmtu;
|
|
tp->mss_cache = mss_now;
|
|
|
|
return mss_now;
|
|
}
|
|
|
|
/* Compute the current effective MSS, taking SACKs and IP options,
|
|
* and even PMTU discovery events into account.
|
|
*
|
|
* LARGESEND note: !urg_mode is overkill, only frames up to snd_up
|
|
* cannot be large. However, taking into account rare use of URG, this
|
|
* is not a big flaw.
|
|
*/
|
|
unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct dst_entry *dst = __sk_dst_get(sk);
|
|
u32 mss_now;
|
|
u16 xmit_size_goal;
|
|
int doing_tso = 0;
|
|
|
|
mss_now = tp->mss_cache;
|
|
|
|
if (large_allowed &&
|
|
(sk->sk_route_caps & NETIF_F_TSO) &&
|
|
!tp->urg_mode)
|
|
doing_tso = 1;
|
|
|
|
if (dst) {
|
|
u32 mtu = dst_mtu(dst);
|
|
if (mtu != tp->pmtu_cookie)
|
|
mss_now = tcp_sync_mss(sk, mtu);
|
|
}
|
|
|
|
if (tp->rx_opt.eff_sacks)
|
|
mss_now -= (TCPOLEN_SACK_BASE_ALIGNED +
|
|
(tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK));
|
|
|
|
xmit_size_goal = mss_now;
|
|
|
|
if (doing_tso) {
|
|
xmit_size_goal = 65535 -
|
|
tp->af_specific->net_header_len -
|
|
tp->ext_header_len - tp->tcp_header_len;
|
|
|
|
if (tp->max_window &&
|
|
(xmit_size_goal > (tp->max_window >> 1)))
|
|
xmit_size_goal = max((tp->max_window >> 1),
|
|
68U - tp->tcp_header_len);
|
|
|
|
xmit_size_goal -= (xmit_size_goal % mss_now);
|
|
}
|
|
tp->xmit_size_goal = xmit_size_goal;
|
|
|
|
return mss_now;
|
|
}
|
|
|
|
/* Congestion window validation. (RFC2861) */
|
|
|
|
static inline void tcp_cwnd_validate(struct sock *sk, struct tcp_sock *tp)
|
|
{
|
|
__u32 packets_out = tp->packets_out;
|
|
|
|
if (packets_out >= tp->snd_cwnd) {
|
|
/* Network is feed fully. */
|
|
tp->snd_cwnd_used = 0;
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
} else {
|
|
/* Network starves. */
|
|
if (tp->packets_out > tp->snd_cwnd_used)
|
|
tp->snd_cwnd_used = tp->packets_out;
|
|
|
|
if ((s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
|
|
tcp_cwnd_application_limited(sk);
|
|
}
|
|
}
|
|
|
|
static unsigned int tcp_window_allows(struct tcp_sock *tp, struct sk_buff *skb, unsigned int mss_now, unsigned int cwnd)
|
|
{
|
|
u32 window, cwnd_len;
|
|
|
|
window = (tp->snd_una + tp->snd_wnd - TCP_SKB_CB(skb)->seq);
|
|
cwnd_len = mss_now * cwnd;
|
|
return min(window, cwnd_len);
|
|
}
|
|
|
|
/* Can at least one segment of SKB be sent right now, according to the
|
|
* congestion window rules? If so, return how many segments are allowed.
|
|
*/
|
|
static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp, struct sk_buff *skb)
|
|
{
|
|
u32 in_flight, cwnd;
|
|
|
|
/* Don't be strict about the congestion window for the final FIN. */
|
|
if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)
|
|
return 1;
|
|
|
|
in_flight = tcp_packets_in_flight(tp);
|
|
cwnd = tp->snd_cwnd;
|
|
if (in_flight < cwnd)
|
|
return (cwnd - in_flight);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* This must be invoked the first time we consider transmitting
|
|
* SKB onto the wire.
|
|
*/
|
|
static inline int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
|
|
{
|
|
int tso_segs = tcp_skb_pcount(skb);
|
|
|
|
if (!tso_segs ||
|
|
(tso_segs > 1 &&
|
|
skb_shinfo(skb)->tso_size != mss_now)) {
|
|
tcp_set_skb_tso_segs(sk, skb, mss_now);
|
|
tso_segs = tcp_skb_pcount(skb);
|
|
}
|
|
return tso_segs;
|
|
}
|
|
|
|
static inline int tcp_minshall_check(const struct tcp_sock *tp)
|
|
{
|
|
return after(tp->snd_sml,tp->snd_una) &&
|
|
!after(tp->snd_sml, tp->snd_nxt);
|
|
}
|
|
|
|
/* Return 0, if packet can be sent now without violation Nagle's rules:
|
|
* 1. It is full sized.
|
|
* 2. Or it contains FIN. (already checked by caller)
|
|
* 3. Or TCP_NODELAY was set.
|
|
* 4. Or TCP_CORK is not set, and all sent packets are ACKed.
|
|
* With Minshall's modification: all sent small packets are ACKed.
|
|
*/
|
|
|
|
static inline int tcp_nagle_check(const struct tcp_sock *tp,
|
|
const struct sk_buff *skb,
|
|
unsigned mss_now, int nonagle)
|
|
{
|
|
return (skb->len < mss_now &&
|
|
((nonagle&TCP_NAGLE_CORK) ||
|
|
(!nonagle &&
|
|
tp->packets_out &&
|
|
tcp_minshall_check(tp))));
|
|
}
|
|
|
|
/* Return non-zero if the Nagle test allows this packet to be
|
|
* sent now.
|
|
*/
|
|
static inline int tcp_nagle_test(struct tcp_sock *tp, struct sk_buff *skb,
|
|
unsigned int cur_mss, int nonagle)
|
|
{
|
|
/* Nagle rule does not apply to frames, which sit in the middle of the
|
|
* write_queue (they have no chances to get new data).
|
|
*
|
|
* This is implemented in the callers, where they modify the 'nonagle'
|
|
* argument based upon the location of SKB in the send queue.
|
|
*/
|
|
if (nonagle & TCP_NAGLE_PUSH)
|
|
return 1;
|
|
|
|
/* Don't use the nagle rule for urgent data (or for the final FIN). */
|
|
if (tp->urg_mode ||
|
|
(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN))
|
|
return 1;
|
|
|
|
if (!tcp_nagle_check(tp, skb, cur_mss, nonagle))
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* Does at least the first segment of SKB fit into the send window? */
|
|
static inline int tcp_snd_wnd_test(struct tcp_sock *tp, struct sk_buff *skb, unsigned int cur_mss)
|
|
{
|
|
u32 end_seq = TCP_SKB_CB(skb)->end_seq;
|
|
|
|
if (skb->len > cur_mss)
|
|
end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
|
|
|
|
return !after(end_seq, tp->snd_una + tp->snd_wnd);
|
|
}
|
|
|
|
/* This checks if the data bearing packet SKB (usually sk->sk_send_head)
|
|
* should be put on the wire right now. If so, it returns the number of
|
|
* packets allowed by the congestion window.
|
|
*/
|
|
static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb,
|
|
unsigned int cur_mss, int nonagle)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
unsigned int cwnd_quota;
|
|
|
|
tcp_init_tso_segs(sk, skb, cur_mss);
|
|
|
|
if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
|
|
return 0;
|
|
|
|
cwnd_quota = tcp_cwnd_test(tp, skb);
|
|
if (cwnd_quota &&
|
|
!tcp_snd_wnd_test(tp, skb, cur_mss))
|
|
cwnd_quota = 0;
|
|
|
|
return cwnd_quota;
|
|
}
|
|
|
|
static inline int tcp_skb_is_last(const struct sock *sk,
|
|
const struct sk_buff *skb)
|
|
{
|
|
return skb->next == (struct sk_buff *)&sk->sk_write_queue;
|
|
}
|
|
|
|
int tcp_may_send_now(struct sock *sk, struct tcp_sock *tp)
|
|
{
|
|
struct sk_buff *skb = sk->sk_send_head;
|
|
|
|
return (skb &&
|
|
tcp_snd_test(sk, skb, tcp_current_mss(sk, 1),
|
|
(tcp_skb_is_last(sk, skb) ?
|
|
TCP_NAGLE_PUSH :
|
|
tp->nonagle)));
|
|
}
|
|
|
|
/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
|
|
* which is put after SKB on the list. It is very much like
|
|
* tcp_fragment() except that it may make several kinds of assumptions
|
|
* in order to speed up the splitting operation. In particular, we
|
|
* know that all the data is in scatter-gather pages, and that the
|
|
* packet has never been sent out before (and thus is not cloned).
|
|
*/
|
|
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, unsigned int mss_now)
|
|
{
|
|
struct sk_buff *buff;
|
|
int nlen = skb->len - len;
|
|
u16 flags;
|
|
|
|
/* All of a TSO frame must be composed of paged data. */
|
|
if (skb->len != skb->data_len)
|
|
return tcp_fragment(sk, skb, len, mss_now);
|
|
|
|
buff = sk_stream_alloc_pskb(sk, 0, 0, GFP_ATOMIC);
|
|
if (unlikely(buff == NULL))
|
|
return -ENOMEM;
|
|
|
|
buff->truesize = nlen;
|
|
skb->truesize -= nlen;
|
|
|
|
/* Correct the sequence numbers. */
|
|
TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
|
|
TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
|
|
TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
|
|
|
|
/* PSH and FIN should only be set in the second packet. */
|
|
flags = TCP_SKB_CB(skb)->flags;
|
|
TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
|
|
TCP_SKB_CB(buff)->flags = flags;
|
|
|
|
/* This packet was never sent out yet, so no SACK bits. */
|
|
TCP_SKB_CB(buff)->sacked = 0;
|
|
|
|
buff->ip_summed = skb->ip_summed = CHECKSUM_HW;
|
|
skb_split(skb, buff, len);
|
|
|
|
/* Fix up tso_factor for both original and new SKB. */
|
|
tcp_set_skb_tso_segs(sk, skb, mss_now);
|
|
tcp_set_skb_tso_segs(sk, buff, mss_now);
|
|
|
|
/* Link BUFF into the send queue. */
|
|
skb_header_release(buff);
|
|
__skb_append(skb, buff, &sk->sk_write_queue);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* Try to defer sending, if possible, in order to minimize the amount
|
|
* of TSO splitting we do. View it as a kind of TSO Nagle test.
|
|
*
|
|
* This algorithm is from John Heffner.
|
|
*/
|
|
static int tcp_tso_should_defer(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
u32 send_win, cong_win, limit, in_flight;
|
|
|
|
if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)
|
|
return 0;
|
|
|
|
if (icsk->icsk_ca_state != TCP_CA_Open)
|
|
return 0;
|
|
|
|
in_flight = tcp_packets_in_flight(tp);
|
|
|
|
BUG_ON(tcp_skb_pcount(skb) <= 1 ||
|
|
(tp->snd_cwnd <= in_flight));
|
|
|
|
send_win = (tp->snd_una + tp->snd_wnd) - TCP_SKB_CB(skb)->seq;
|
|
|
|
/* From in_flight test above, we know that cwnd > in_flight. */
|
|
cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
|
|
|
|
limit = min(send_win, cong_win);
|
|
|
|
if (sysctl_tcp_tso_win_divisor) {
|
|
u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
|
|
|
|
/* If at least some fraction of a window is available,
|
|
* just use it.
|
|
*/
|
|
chunk /= sysctl_tcp_tso_win_divisor;
|
|
if (limit >= chunk)
|
|
return 0;
|
|
} else {
|
|
/* Different approach, try not to defer past a single
|
|
* ACK. Receiver should ACK every other full sized
|
|
* frame, so if we have space for more than 3 frames
|
|
* then send now.
|
|
*/
|
|
if (limit > tcp_max_burst(tp) * tp->mss_cache)
|
|
return 0;
|
|
}
|
|
|
|
/* Ok, it looks like it is advisable to defer. */
|
|
return 1;
|
|
}
|
|
|
|
/* This routine writes packets to the network. It advances the
|
|
* send_head. This happens as incoming acks open up the remote
|
|
* window for us.
|
|
*
|
|
* Returns 1, if no segments are in flight and we have queued segments, but
|
|
* cannot send anything now because of SWS or another problem.
|
|
*/
|
|
static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
unsigned int tso_segs, sent_pkts;
|
|
int cwnd_quota;
|
|
|
|
/* If we are closed, the bytes will have to remain here.
|
|
* In time closedown will finish, we empty the write queue and all
|
|
* will be happy.
|
|
*/
|
|
if (unlikely(sk->sk_state == TCP_CLOSE))
|
|
return 0;
|
|
|
|
sent_pkts = 0;
|
|
while ((skb = sk->sk_send_head)) {
|
|
unsigned int limit;
|
|
|
|
tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
|
|
BUG_ON(!tso_segs);
|
|
|
|
cwnd_quota = tcp_cwnd_test(tp, skb);
|
|
if (!cwnd_quota)
|
|
break;
|
|
|
|
if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
|
|
break;
|
|
|
|
if (tso_segs == 1) {
|
|
if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
|
|
(tcp_skb_is_last(sk, skb) ?
|
|
nonagle : TCP_NAGLE_PUSH))))
|
|
break;
|
|
} else {
|
|
if (tcp_tso_should_defer(sk, tp, skb))
|
|
break;
|
|
}
|
|
|
|
limit = mss_now;
|
|
if (tso_segs > 1) {
|
|
limit = tcp_window_allows(tp, skb,
|
|
mss_now, cwnd_quota);
|
|
|
|
if (skb->len < limit) {
|
|
unsigned int trim = skb->len % mss_now;
|
|
|
|
if (trim)
|
|
limit = skb->len - trim;
|
|
}
|
|
}
|
|
|
|
if (skb->len > limit &&
|
|
unlikely(tso_fragment(sk, skb, limit, mss_now)))
|
|
break;
|
|
|
|
TCP_SKB_CB(skb)->when = tcp_time_stamp;
|
|
|
|
if (unlikely(tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC))))
|
|
break;
|
|
|
|
/* Advance the send_head. This one is sent out.
|
|
* This call will increment packets_out.
|
|
*/
|
|
update_send_head(sk, tp, skb);
|
|
|
|
tcp_minshall_update(tp, mss_now, skb);
|
|
sent_pkts++;
|
|
}
|
|
|
|
if (likely(sent_pkts)) {
|
|
tcp_cwnd_validate(sk, tp);
|
|
return 0;
|
|
}
|
|
return !tp->packets_out && sk->sk_send_head;
|
|
}
|
|
|
|
/* Push out any pending frames which were held back due to
|
|
* TCP_CORK or attempt at coalescing tiny packets.
|
|
* The socket must be locked by the caller.
|
|
*/
|
|
void __tcp_push_pending_frames(struct sock *sk, struct tcp_sock *tp,
|
|
unsigned int cur_mss, int nonagle)
|
|
{
|
|
struct sk_buff *skb = sk->sk_send_head;
|
|
|
|
if (skb) {
|
|
if (tcp_write_xmit(sk, cur_mss, nonagle))
|
|
tcp_check_probe_timer(sk, tp);
|
|
}
|
|
}
|
|
|
|
/* Send _single_ skb sitting at the send head. This function requires
|
|
* true push pending frames to setup probe timer etc.
|
|
*/
|
|
void tcp_push_one(struct sock *sk, unsigned int mss_now)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb = sk->sk_send_head;
|
|
unsigned int tso_segs, cwnd_quota;
|
|
|
|
BUG_ON(!skb || skb->len < mss_now);
|
|
|
|
tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
|
|
cwnd_quota = tcp_snd_test(sk, skb, mss_now, TCP_NAGLE_PUSH);
|
|
|
|
if (likely(cwnd_quota)) {
|
|
unsigned int limit;
|
|
|
|
BUG_ON(!tso_segs);
|
|
|
|
limit = mss_now;
|
|
if (tso_segs > 1) {
|
|
limit = tcp_window_allows(tp, skb,
|
|
mss_now, cwnd_quota);
|
|
|
|
if (skb->len < limit) {
|
|
unsigned int trim = skb->len % mss_now;
|
|
|
|
if (trim)
|
|
limit = skb->len - trim;
|
|
}
|
|
}
|
|
|
|
if (skb->len > limit &&
|
|
unlikely(tso_fragment(sk, skb, limit, mss_now)))
|
|
return;
|
|
|
|
/* Send it out now. */
|
|
TCP_SKB_CB(skb)->when = tcp_time_stamp;
|
|
|
|
if (likely(!tcp_transmit_skb(sk, skb_clone(skb, sk->sk_allocation)))) {
|
|
update_send_head(sk, tp, skb);
|
|
tcp_cwnd_validate(sk, tp);
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* This function returns the amount that we can raise the
|
|
* usable window based on the following constraints
|
|
*
|
|
* 1. The window can never be shrunk once it is offered (RFC 793)
|
|
* 2. We limit memory per socket
|
|
*
|
|
* RFC 1122:
|
|
* "the suggested [SWS] avoidance algorithm for the receiver is to keep
|
|
* RECV.NEXT + RCV.WIN fixed until:
|
|
* RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
|
|
*
|
|
* i.e. don't raise the right edge of the window until you can raise
|
|
* it at least MSS bytes.
|
|
*
|
|
* Unfortunately, the recommended algorithm breaks header prediction,
|
|
* since header prediction assumes th->window stays fixed.
|
|
*
|
|
* Strictly speaking, keeping th->window fixed violates the receiver
|
|
* side SWS prevention criteria. The problem is that under this rule
|
|
* a stream of single byte packets will cause the right side of the
|
|
* window to always advance by a single byte.
|
|
*
|
|
* Of course, if the sender implements sender side SWS prevention
|
|
* then this will not be a problem.
|
|
*
|
|
* BSD seems to make the following compromise:
|
|
*
|
|
* If the free space is less than the 1/4 of the maximum
|
|
* space available and the free space is less than 1/2 mss,
|
|
* then set the window to 0.
|
|
* [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
|
|
* Otherwise, just prevent the window from shrinking
|
|
* and from being larger than the largest representable value.
|
|
*
|
|
* This prevents incremental opening of the window in the regime
|
|
* where TCP is limited by the speed of the reader side taking
|
|
* data out of the TCP receive queue. It does nothing about
|
|
* those cases where the window is constrained on the sender side
|
|
* because the pipeline is full.
|
|
*
|
|
* BSD also seems to "accidentally" limit itself to windows that are a
|
|
* multiple of MSS, at least until the free space gets quite small.
|
|
* This would appear to be a side effect of the mbuf implementation.
|
|
* Combining these two algorithms results in the observed behavior
|
|
* of having a fixed window size at almost all times.
|
|
*
|
|
* Below we obtain similar behavior by forcing the offered window to
|
|
* a multiple of the mss when it is feasible to do so.
|
|
*
|
|
* Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
|
|
* Regular options like TIMESTAMP are taken into account.
|
|
*/
|
|
u32 __tcp_select_window(struct sock *sk)
|
|
{
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
/* MSS for the peer's data. Previous verions used mss_clamp
|
|
* here. I don't know if the value based on our guesses
|
|
* of peer's MSS is better for the performance. It's more correct
|
|
* but may be worse for the performance because of rcv_mss
|
|
* fluctuations. --SAW 1998/11/1
|
|
*/
|
|
int mss = icsk->icsk_ack.rcv_mss;
|
|
int free_space = tcp_space(sk);
|
|
int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk));
|
|
int window;
|
|
|
|
if (mss > full_space)
|
|
mss = full_space;
|
|
|
|
if (free_space < full_space/2) {
|
|
icsk->icsk_ack.quick = 0;
|
|
|
|
if (tcp_memory_pressure)
|
|
tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U*tp->advmss);
|
|
|
|
if (free_space < mss)
|
|
return 0;
|
|
}
|
|
|
|
if (free_space > tp->rcv_ssthresh)
|
|
free_space = tp->rcv_ssthresh;
|
|
|
|
/* Don't do rounding if we are using window scaling, since the
|
|
* scaled window will not line up with the MSS boundary anyway.
|
|
*/
|
|
window = tp->rcv_wnd;
|
|
if (tp->rx_opt.rcv_wscale) {
|
|
window = free_space;
|
|
|
|
/* Advertise enough space so that it won't get scaled away.
|
|
* Import case: prevent zero window announcement if
|
|
* 1<<rcv_wscale > mss.
|
|
*/
|
|
if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
|
|
window = (((window >> tp->rx_opt.rcv_wscale) + 1)
|
|
<< tp->rx_opt.rcv_wscale);
|
|
} else {
|
|
/* Get the largest window that is a nice multiple of mss.
|
|
* Window clamp already applied above.
|
|
* If our current window offering is within 1 mss of the
|
|
* free space we just keep it. This prevents the divide
|
|
* and multiply from happening most of the time.
|
|
* We also don't do any window rounding when the free space
|
|
* is too small.
|
|
*/
|
|
if (window <= free_space - mss || window > free_space)
|
|
window = (free_space/mss)*mss;
|
|
}
|
|
|
|
return window;
|
|
}
|
|
|
|
/* Attempt to collapse two adjacent SKB's during retransmission. */
|
|
static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int mss_now)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *next_skb = skb->next;
|
|
|
|
/* The first test we must make is that neither of these two
|
|
* SKB's are still referenced by someone else.
|
|
*/
|
|
if (!skb_cloned(skb) && !skb_cloned(next_skb)) {
|
|
int skb_size = skb->len, next_skb_size = next_skb->len;
|
|
u16 flags = TCP_SKB_CB(skb)->flags;
|
|
|
|
/* Also punt if next skb has been SACK'd. */
|
|
if(TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_ACKED)
|
|
return;
|
|
|
|
/* Next skb is out of window. */
|
|
if (after(TCP_SKB_CB(next_skb)->end_seq, tp->snd_una+tp->snd_wnd))
|
|
return;
|
|
|
|
/* Punt if not enough space exists in the first SKB for
|
|
* the data in the second, or the total combined payload
|
|
* would exceed the MSS.
|
|
*/
|
|
if ((next_skb_size > skb_tailroom(skb)) ||
|
|
((skb_size + next_skb_size) > mss_now))
|
|
return;
|
|
|
|
BUG_ON(tcp_skb_pcount(skb) != 1 ||
|
|
tcp_skb_pcount(next_skb) != 1);
|
|
|
|
/* Ok. We will be able to collapse the packet. */
|
|
__skb_unlink(next_skb, &sk->sk_write_queue);
|
|
|
|
memcpy(skb_put(skb, next_skb_size), next_skb->data, next_skb_size);
|
|
|
|
if (next_skb->ip_summed == CHECKSUM_HW)
|
|
skb->ip_summed = CHECKSUM_HW;
|
|
|
|
if (skb->ip_summed != CHECKSUM_HW)
|
|
skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
|
|
|
|
/* Update sequence range on original skb. */
|
|
TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
|
|
|
|
/* Merge over control information. */
|
|
flags |= TCP_SKB_CB(next_skb)->flags; /* This moves PSH/FIN etc. over */
|
|
TCP_SKB_CB(skb)->flags = flags;
|
|
|
|
/* All done, get rid of second SKB and account for it so
|
|
* packet counting does not break.
|
|
*/
|
|
TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked&(TCPCB_EVER_RETRANS|TCPCB_AT_TAIL);
|
|
if (TCP_SKB_CB(next_skb)->sacked&TCPCB_SACKED_RETRANS)
|
|
tp->retrans_out -= tcp_skb_pcount(next_skb);
|
|
if (TCP_SKB_CB(next_skb)->sacked&TCPCB_LOST) {
|
|
tp->lost_out -= tcp_skb_pcount(next_skb);
|
|
tp->left_out -= tcp_skb_pcount(next_skb);
|
|
}
|
|
/* Reno case is special. Sigh... */
|
|
if (!tp->rx_opt.sack_ok && tp->sacked_out) {
|
|
tcp_dec_pcount_approx(&tp->sacked_out, next_skb);
|
|
tp->left_out -= tcp_skb_pcount(next_skb);
|
|
}
|
|
|
|
/* Not quite right: it can be > snd.fack, but
|
|
* it is better to underestimate fackets.
|
|
*/
|
|
tcp_dec_pcount_approx(&tp->fackets_out, next_skb);
|
|
tcp_packets_out_dec(tp, next_skb);
|
|
sk_stream_free_skb(sk, next_skb);
|
|
}
|
|
}
|
|
|
|
/* Do a simple retransmit without using the backoff mechanisms in
|
|
* tcp_timer. This is used for path mtu discovery.
|
|
* The socket is already locked here.
|
|
*/
|
|
void tcp_simple_retransmit(struct sock *sk)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
unsigned int mss = tcp_current_mss(sk, 0);
|
|
int lost = 0;
|
|
|
|
sk_stream_for_retrans_queue(skb, sk) {
|
|
if (skb->len > mss &&
|
|
!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
|
|
if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) {
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
|
|
tp->retrans_out -= tcp_skb_pcount(skb);
|
|
}
|
|
if (!(TCP_SKB_CB(skb)->sacked&TCPCB_LOST)) {
|
|
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
|
|
tp->lost_out += tcp_skb_pcount(skb);
|
|
lost = 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!lost)
|
|
return;
|
|
|
|
tcp_sync_left_out(tp);
|
|
|
|
/* Don't muck with the congestion window here.
|
|
* Reason is that we do not increase amount of _data_
|
|
* in network, but units changed and effective
|
|
* cwnd/ssthresh really reduced now.
|
|
*/
|
|
if (icsk->icsk_ca_state != TCP_CA_Loss) {
|
|
tp->high_seq = tp->snd_nxt;
|
|
tp->snd_ssthresh = tcp_current_ssthresh(sk);
|
|
tp->prior_ssthresh = 0;
|
|
tp->undo_marker = 0;
|
|
tcp_set_ca_state(sk, TCP_CA_Loss);
|
|
}
|
|
tcp_xmit_retransmit_queue(sk);
|
|
}
|
|
|
|
/* This retransmits one SKB. Policy decisions and retransmit queue
|
|
* state updates are done by the caller. Returns non-zero if an
|
|
* error occurred which prevented the send.
|
|
*/
|
|
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
unsigned int cur_mss = tcp_current_mss(sk, 0);
|
|
int err;
|
|
|
|
/* Do not sent more than we queued. 1/4 is reserved for possible
|
|
* copying overhead: frgagmentation, tunneling, mangling etc.
|
|
*/
|
|
if (atomic_read(&sk->sk_wmem_alloc) >
|
|
min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
|
|
return -EAGAIN;
|
|
|
|
if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
|
|
if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
|
|
BUG();
|
|
if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
|
|
return -ENOMEM;
|
|
}
|
|
|
|
/* If receiver has shrunk his window, and skb is out of
|
|
* new window, do not retransmit it. The exception is the
|
|
* case, when window is shrunk to zero. In this case
|
|
* our retransmit serves as a zero window probe.
|
|
*/
|
|
if (!before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)
|
|
&& TCP_SKB_CB(skb)->seq != tp->snd_una)
|
|
return -EAGAIN;
|
|
|
|
if (skb->len > cur_mss) {
|
|
if (tcp_fragment(sk, skb, cur_mss, cur_mss))
|
|
return -ENOMEM; /* We'll try again later. */
|
|
}
|
|
|
|
/* Collapse two adjacent packets if worthwhile and we can. */
|
|
if(!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) &&
|
|
(skb->len < (cur_mss >> 1)) &&
|
|
(skb->next != sk->sk_send_head) &&
|
|
(skb->next != (struct sk_buff *)&sk->sk_write_queue) &&
|
|
(skb_shinfo(skb)->nr_frags == 0 && skb_shinfo(skb->next)->nr_frags == 0) &&
|
|
(tcp_skb_pcount(skb) == 1 && tcp_skb_pcount(skb->next) == 1) &&
|
|
(sysctl_tcp_retrans_collapse != 0))
|
|
tcp_retrans_try_collapse(sk, skb, cur_mss);
|
|
|
|
if(tp->af_specific->rebuild_header(sk))
|
|
return -EHOSTUNREACH; /* Routing failure or similar. */
|
|
|
|
/* Some Solaris stacks overoptimize and ignore the FIN on a
|
|
* retransmit when old data is attached. So strip it off
|
|
* since it is cheap to do so and saves bytes on the network.
|
|
*/
|
|
if(skb->len > 0 &&
|
|
(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) &&
|
|
tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) {
|
|
if (!pskb_trim(skb, 0)) {
|
|
TCP_SKB_CB(skb)->seq = TCP_SKB_CB(skb)->end_seq - 1;
|
|
skb_shinfo(skb)->tso_segs = 1;
|
|
skb_shinfo(skb)->tso_size = 0;
|
|
skb->ip_summed = CHECKSUM_NONE;
|
|
skb->csum = 0;
|
|
}
|
|
}
|
|
|
|
/* Make a copy, if the first transmission SKB clone we made
|
|
* is still in somebody's hands, else make a clone.
|
|
*/
|
|
TCP_SKB_CB(skb)->when = tcp_time_stamp;
|
|
|
|
err = tcp_transmit_skb(sk, (skb_cloned(skb) ?
|
|
pskb_copy(skb, GFP_ATOMIC):
|
|
skb_clone(skb, GFP_ATOMIC)));
|
|
|
|
if (err == 0) {
|
|
/* Update global TCP statistics. */
|
|
TCP_INC_STATS(TCP_MIB_RETRANSSEGS);
|
|
|
|
tp->total_retrans++;
|
|
|
|
#if FASTRETRANS_DEBUG > 0
|
|
if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) {
|
|
if (net_ratelimit())
|
|
printk(KERN_DEBUG "retrans_out leaked.\n");
|
|
}
|
|
#endif
|
|
TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
|
|
tp->retrans_out += tcp_skb_pcount(skb);
|
|
|
|
/* Save stamp of the first retransmit. */
|
|
if (!tp->retrans_stamp)
|
|
tp->retrans_stamp = TCP_SKB_CB(skb)->when;
|
|
|
|
tp->undo_retrans++;
|
|
|
|
/* snd_nxt is stored to detect loss of retransmitted segment,
|
|
* see tcp_input.c tcp_sacktag_write_queue().
|
|
*/
|
|
TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt;
|
|
}
|
|
return err;
|
|
}
|
|
|
|
/* This gets called after a retransmit timeout, and the initially
|
|
* retransmitted data is acknowledged. It tries to continue
|
|
* resending the rest of the retransmit queue, until either
|
|
* we've sent it all or the congestion window limit is reached.
|
|
* If doing SACK, the first ACK which comes back for a timeout
|
|
* based retransmit packet might feed us FACK information again.
|
|
* If so, we use it to avoid unnecessarily retransmissions.
|
|
*/
|
|
void tcp_xmit_retransmit_queue(struct sock *sk)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
int packet_cnt = tp->lost_out;
|
|
|
|
/* First pass: retransmit lost packets. */
|
|
if (packet_cnt) {
|
|
sk_stream_for_retrans_queue(skb, sk) {
|
|
__u8 sacked = TCP_SKB_CB(skb)->sacked;
|
|
|
|
/* Assume this retransmit will generate
|
|
* only one packet for congestion window
|
|
* calculation purposes. This works because
|
|
* tcp_retransmit_skb() will chop up the
|
|
* packet to be MSS sized and all the
|
|
* packet counting works out.
|
|
*/
|
|
if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
|
|
return;
|
|
|
|
if (sacked&TCPCB_LOST) {
|
|
if (!(sacked&(TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) {
|
|
if (tcp_retransmit_skb(sk, skb))
|
|
return;
|
|
if (icsk->icsk_ca_state != TCP_CA_Loss)
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS);
|
|
else
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS);
|
|
|
|
if (skb ==
|
|
skb_peek(&sk->sk_write_queue))
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
|
|
inet_csk(sk)->icsk_rto,
|
|
TCP_RTO_MAX);
|
|
}
|
|
|
|
packet_cnt -= tcp_skb_pcount(skb);
|
|
if (packet_cnt <= 0)
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* OK, demanded retransmission is finished. */
|
|
|
|
/* Forward retransmissions are possible only during Recovery. */
|
|
if (icsk->icsk_ca_state != TCP_CA_Recovery)
|
|
return;
|
|
|
|
/* No forward retransmissions in Reno are possible. */
|
|
if (!tp->rx_opt.sack_ok)
|
|
return;
|
|
|
|
/* Yeah, we have to make difficult choice between forward transmission
|
|
* and retransmission... Both ways have their merits...
|
|
*
|
|
* For now we do not retransmit anything, while we have some new
|
|
* segments to send.
|
|
*/
|
|
|
|
if (tcp_may_send_now(sk, tp))
|
|
return;
|
|
|
|
packet_cnt = 0;
|
|
|
|
sk_stream_for_retrans_queue(skb, sk) {
|
|
/* Similar to the retransmit loop above we
|
|
* can pretend that the retransmitted SKB
|
|
* we send out here will be composed of one
|
|
* real MSS sized packet because tcp_retransmit_skb()
|
|
* will fragment it if necessary.
|
|
*/
|
|
if (++packet_cnt > tp->fackets_out)
|
|
break;
|
|
|
|
if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
|
|
break;
|
|
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS)
|
|
continue;
|
|
|
|
/* Ok, retransmit it. */
|
|
if (tcp_retransmit_skb(sk, skb))
|
|
break;
|
|
|
|
if (skb == skb_peek(&sk->sk_write_queue))
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
|
|
inet_csk(sk)->icsk_rto,
|
|
TCP_RTO_MAX);
|
|
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS);
|
|
}
|
|
}
|
|
|
|
|
|
/* Send a fin. The caller locks the socket for us. This cannot be
|
|
* allowed to fail queueing a FIN frame under any circumstances.
|
|
*/
|
|
void tcp_send_fin(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb = skb_peek_tail(&sk->sk_write_queue);
|
|
int mss_now;
|
|
|
|
/* Optimization, tack on the FIN if we have a queue of
|
|
* unsent frames. But be careful about outgoing SACKS
|
|
* and IP options.
|
|
*/
|
|
mss_now = tcp_current_mss(sk, 1);
|
|
|
|
if (sk->sk_send_head != NULL) {
|
|
TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN;
|
|
TCP_SKB_CB(skb)->end_seq++;
|
|
tp->write_seq++;
|
|
} else {
|
|
/* Socket is locked, keep trying until memory is available. */
|
|
for (;;) {
|
|
skb = alloc_skb_fclone(MAX_TCP_HEADER, GFP_KERNEL);
|
|
if (skb)
|
|
break;
|
|
yield();
|
|
}
|
|
|
|
/* Reserve space for headers and prepare control bits. */
|
|
skb_reserve(skb, MAX_TCP_HEADER);
|
|
skb->csum = 0;
|
|
TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_FIN);
|
|
TCP_SKB_CB(skb)->sacked = 0;
|
|
skb_shinfo(skb)->tso_segs = 1;
|
|
skb_shinfo(skb)->tso_size = 0;
|
|
|
|
/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
|
|
TCP_SKB_CB(skb)->seq = tp->write_seq;
|
|
TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1;
|
|
tcp_queue_skb(sk, skb);
|
|
}
|
|
__tcp_push_pending_frames(sk, tp, mss_now, TCP_NAGLE_OFF);
|
|
}
|
|
|
|
/* We get here when a process closes a file descriptor (either due to
|
|
* an explicit close() or as a byproduct of exit()'ing) and there
|
|
* was unread data in the receive queue. This behavior is recommended
|
|
* by draft-ietf-tcpimpl-prob-03.txt section 3.10. -DaveM
|
|
*/
|
|
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
|
|
/* NOTE: No TCP options attached and we never retransmit this. */
|
|
skb = alloc_skb(MAX_TCP_HEADER, priority);
|
|
if (!skb) {
|
|
NET_INC_STATS(LINUX_MIB_TCPABORTFAILED);
|
|
return;
|
|
}
|
|
|
|
/* Reserve space for headers and prepare control bits. */
|
|
skb_reserve(skb, MAX_TCP_HEADER);
|
|
skb->csum = 0;
|
|
TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_RST);
|
|
TCP_SKB_CB(skb)->sacked = 0;
|
|
skb_shinfo(skb)->tso_segs = 1;
|
|
skb_shinfo(skb)->tso_size = 0;
|
|
|
|
/* Send it off. */
|
|
TCP_SKB_CB(skb)->seq = tcp_acceptable_seq(sk, tp);
|
|
TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq;
|
|
TCP_SKB_CB(skb)->when = tcp_time_stamp;
|
|
if (tcp_transmit_skb(sk, skb))
|
|
NET_INC_STATS(LINUX_MIB_TCPABORTFAILED);
|
|
}
|
|
|
|
/* WARNING: This routine must only be called when we have already sent
|
|
* a SYN packet that crossed the incoming SYN that caused this routine
|
|
* to get called. If this assumption fails then the initial rcv_wnd
|
|
* and rcv_wscale values will not be correct.
|
|
*/
|
|
int tcp_send_synack(struct sock *sk)
|
|
{
|
|
struct sk_buff* skb;
|
|
|
|
skb = skb_peek(&sk->sk_write_queue);
|
|
if (skb == NULL || !(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_SYN)) {
|
|
printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n");
|
|
return -EFAULT;
|
|
}
|
|
if (!(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_ACK)) {
|
|
if (skb_cloned(skb)) {
|
|
struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
|
|
if (nskb == NULL)
|
|
return -ENOMEM;
|
|
__skb_unlink(skb, &sk->sk_write_queue);
|
|
skb_header_release(nskb);
|
|
__skb_queue_head(&sk->sk_write_queue, nskb);
|
|
sk_stream_free_skb(sk, skb);
|
|
sk_charge_skb(sk, nskb);
|
|
skb = nskb;
|
|
}
|
|
|
|
TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ACK;
|
|
TCP_ECN_send_synack(tcp_sk(sk), skb);
|
|
}
|
|
TCP_SKB_CB(skb)->when = tcp_time_stamp;
|
|
return tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC));
|
|
}
|
|
|
|
/*
|
|
* Prepare a SYN-ACK.
|
|
*/
|
|
struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,
|
|
struct request_sock *req)
|
|
{
|
|
struct inet_request_sock *ireq = inet_rsk(req);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct tcphdr *th;
|
|
int tcp_header_size;
|
|
struct sk_buff *skb;
|
|
|
|
skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC);
|
|
if (skb == NULL)
|
|
return NULL;
|
|
|
|
/* Reserve space for headers. */
|
|
skb_reserve(skb, MAX_TCP_HEADER);
|
|
|
|
skb->dst = dst_clone(dst);
|
|
|
|
tcp_header_size = (sizeof(struct tcphdr) + TCPOLEN_MSS +
|
|
(ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) +
|
|
(ireq->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) +
|
|
/* SACK_PERM is in the place of NOP NOP of TS */
|
|
((ireq->sack_ok && !ireq->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0));
|
|
skb->h.th = th = (struct tcphdr *) skb_push(skb, tcp_header_size);
|
|
|
|
memset(th, 0, sizeof(struct tcphdr));
|
|
th->syn = 1;
|
|
th->ack = 1;
|
|
if (dst->dev->features&NETIF_F_TSO)
|
|
ireq->ecn_ok = 0;
|
|
TCP_ECN_make_synack(req, th);
|
|
th->source = inet_sk(sk)->sport;
|
|
th->dest = ireq->rmt_port;
|
|
TCP_SKB_CB(skb)->seq = tcp_rsk(req)->snt_isn;
|
|
TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1;
|
|
TCP_SKB_CB(skb)->sacked = 0;
|
|
skb_shinfo(skb)->tso_segs = 1;
|
|
skb_shinfo(skb)->tso_size = 0;
|
|
th->seq = htonl(TCP_SKB_CB(skb)->seq);
|
|
th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
|
|
if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
|
|
__u8 rcv_wscale;
|
|
/* Set this up on the first call only */
|
|
req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
|
|
/* tcp_full_space because it is guaranteed to be the first packet */
|
|
tcp_select_initial_window(tcp_full_space(sk),
|
|
dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
|
|
&req->rcv_wnd,
|
|
&req->window_clamp,
|
|
ireq->wscale_ok,
|
|
&rcv_wscale);
|
|
ireq->rcv_wscale = rcv_wscale;
|
|
}
|
|
|
|
/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
|
|
th->window = htons(req->rcv_wnd);
|
|
|
|
TCP_SKB_CB(skb)->when = tcp_time_stamp;
|
|
tcp_syn_build_options((__u32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), ireq->tstamp_ok,
|
|
ireq->sack_ok, ireq->wscale_ok, ireq->rcv_wscale,
|
|
TCP_SKB_CB(skb)->when,
|
|
req->ts_recent);
|
|
|
|
skb->csum = 0;
|
|
th->doff = (tcp_header_size >> 2);
|
|
TCP_INC_STATS(TCP_MIB_OUTSEGS);
|
|
return skb;
|
|
}
|
|
|
|
/*
|
|
* Do all connect socket setups that can be done AF independent.
|
|
*/
|
|
static inline void tcp_connect_init(struct sock *sk)
|
|
{
|
|
struct dst_entry *dst = __sk_dst_get(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
__u8 rcv_wscale;
|
|
|
|
/* We'll fix this up when we get a response from the other end.
|
|
* See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
|
|
*/
|
|
tp->tcp_header_len = sizeof(struct tcphdr) +
|
|
(sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
|
|
|
|
/* If user gave his TCP_MAXSEG, record it to clamp */
|
|
if (tp->rx_opt.user_mss)
|
|
tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
|
|
tp->max_window = 0;
|
|
tcp_sync_mss(sk, dst_mtu(dst));
|
|
|
|
if (!tp->window_clamp)
|
|
tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
|
|
tp->advmss = dst_metric(dst, RTAX_ADVMSS);
|
|
tcp_initialize_rcv_mss(sk);
|
|
|
|
tcp_select_initial_window(tcp_full_space(sk),
|
|
tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
|
|
&tp->rcv_wnd,
|
|
&tp->window_clamp,
|
|
sysctl_tcp_window_scaling,
|
|
&rcv_wscale);
|
|
|
|
tp->rx_opt.rcv_wscale = rcv_wscale;
|
|
tp->rcv_ssthresh = tp->rcv_wnd;
|
|
|
|
sk->sk_err = 0;
|
|
sock_reset_flag(sk, SOCK_DONE);
|
|
tp->snd_wnd = 0;
|
|
tcp_init_wl(tp, tp->write_seq, 0);
|
|
tp->snd_una = tp->write_seq;
|
|
tp->snd_sml = tp->write_seq;
|
|
tp->rcv_nxt = 0;
|
|
tp->rcv_wup = 0;
|
|
tp->copied_seq = 0;
|
|
|
|
inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
|
|
inet_csk(sk)->icsk_retransmits = 0;
|
|
tcp_clear_retrans(tp);
|
|
}
|
|
|
|
/*
|
|
* Build a SYN and send it off.
|
|
*/
|
|
int tcp_connect(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *buff;
|
|
|
|
tcp_connect_init(sk);
|
|
|
|
buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
|
|
if (unlikely(buff == NULL))
|
|
return -ENOBUFS;
|
|
|
|
/* Reserve space for headers. */
|
|
skb_reserve(buff, MAX_TCP_HEADER);
|
|
|
|
TCP_SKB_CB(buff)->flags = TCPCB_FLAG_SYN;
|
|
TCP_ECN_send_syn(sk, tp, buff);
|
|
TCP_SKB_CB(buff)->sacked = 0;
|
|
skb_shinfo(buff)->tso_segs = 1;
|
|
skb_shinfo(buff)->tso_size = 0;
|
|
buff->csum = 0;
|
|
TCP_SKB_CB(buff)->seq = tp->write_seq++;
|
|
TCP_SKB_CB(buff)->end_seq = tp->write_seq;
|
|
tp->snd_nxt = tp->write_seq;
|
|
tp->pushed_seq = tp->write_seq;
|
|
|
|
/* Send it off. */
|
|
TCP_SKB_CB(buff)->when = tcp_time_stamp;
|
|
tp->retrans_stamp = TCP_SKB_CB(buff)->when;
|
|
skb_header_release(buff);
|
|
__skb_queue_tail(&sk->sk_write_queue, buff);
|
|
sk_charge_skb(sk, buff);
|
|
tp->packets_out += tcp_skb_pcount(buff);
|
|
tcp_transmit_skb(sk, skb_clone(buff, GFP_KERNEL));
|
|
TCP_INC_STATS(TCP_MIB_ACTIVEOPENS);
|
|
|
|
/* Timer for repeating the SYN until an answer. */
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
|
|
inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
|
|
return 0;
|
|
}
|
|
|
|
/* Send out a delayed ack, the caller does the policy checking
|
|
* to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
|
|
* for details.
|
|
*/
|
|
void tcp_send_delayed_ack(struct sock *sk)
|
|
{
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
int ato = icsk->icsk_ack.ato;
|
|
unsigned long timeout;
|
|
|
|
if (ato > TCP_DELACK_MIN) {
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
int max_ato = HZ/2;
|
|
|
|
if (icsk->icsk_ack.pingpong || (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
|
|
max_ato = TCP_DELACK_MAX;
|
|
|
|
/* Slow path, intersegment interval is "high". */
|
|
|
|
/* If some rtt estimate is known, use it to bound delayed ack.
|
|
* Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
|
|
* directly.
|
|
*/
|
|
if (tp->srtt) {
|
|
int rtt = max(tp->srtt>>3, TCP_DELACK_MIN);
|
|
|
|
if (rtt < max_ato)
|
|
max_ato = rtt;
|
|
}
|
|
|
|
ato = min(ato, max_ato);
|
|
}
|
|
|
|
/* Stay within the limit we were given */
|
|
timeout = jiffies + ato;
|
|
|
|
/* Use new timeout only if there wasn't a older one earlier. */
|
|
if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
|
|
/* If delack timer was blocked or is about to expire,
|
|
* send ACK now.
|
|
*/
|
|
if (icsk->icsk_ack.blocked ||
|
|
time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
|
|
tcp_send_ack(sk);
|
|
return;
|
|
}
|
|
|
|
if (!time_before(timeout, icsk->icsk_ack.timeout))
|
|
timeout = icsk->icsk_ack.timeout;
|
|
}
|
|
icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
|
|
icsk->icsk_ack.timeout = timeout;
|
|
sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
|
|
}
|
|
|
|
/* This routine sends an ack and also updates the window. */
|
|
void tcp_send_ack(struct sock *sk)
|
|
{
|
|
/* If we have been reset, we may not send again. */
|
|
if (sk->sk_state != TCP_CLOSE) {
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *buff;
|
|
|
|
/* We are not putting this on the write queue, so
|
|
* tcp_transmit_skb() will set the ownership to this
|
|
* sock.
|
|
*/
|
|
buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
|
|
if (buff == NULL) {
|
|
inet_csk_schedule_ack(sk);
|
|
inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
|
|
TCP_DELACK_MAX, TCP_RTO_MAX);
|
|
return;
|
|
}
|
|
|
|
/* Reserve space for headers and prepare control bits. */
|
|
skb_reserve(buff, MAX_TCP_HEADER);
|
|
buff->csum = 0;
|
|
TCP_SKB_CB(buff)->flags = TCPCB_FLAG_ACK;
|
|
TCP_SKB_CB(buff)->sacked = 0;
|
|
skb_shinfo(buff)->tso_segs = 1;
|
|
skb_shinfo(buff)->tso_size = 0;
|
|
|
|
/* Send it off, this clears delayed acks for us. */
|
|
TCP_SKB_CB(buff)->seq = TCP_SKB_CB(buff)->end_seq = tcp_acceptable_seq(sk, tp);
|
|
TCP_SKB_CB(buff)->when = tcp_time_stamp;
|
|
tcp_transmit_skb(sk, buff);
|
|
}
|
|
}
|
|
|
|
/* This routine sends a packet with an out of date sequence
|
|
* number. It assumes the other end will try to ack it.
|
|
*
|
|
* Question: what should we make while urgent mode?
|
|
* 4.4BSD forces sending single byte of data. We cannot send
|
|
* out of window data, because we have SND.NXT==SND.MAX...
|
|
*
|
|
* Current solution: to send TWO zero-length segments in urgent mode:
|
|
* one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
|
|
* out-of-date with SND.UNA-1 to probe window.
|
|
*/
|
|
static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
|
|
/* We don't queue it, tcp_transmit_skb() sets ownership. */
|
|
skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
|
|
if (skb == NULL)
|
|
return -1;
|
|
|
|
/* Reserve space for headers and set control bits. */
|
|
skb_reserve(skb, MAX_TCP_HEADER);
|
|
skb->csum = 0;
|
|
TCP_SKB_CB(skb)->flags = TCPCB_FLAG_ACK;
|
|
TCP_SKB_CB(skb)->sacked = urgent;
|
|
skb_shinfo(skb)->tso_segs = 1;
|
|
skb_shinfo(skb)->tso_size = 0;
|
|
|
|
/* Use a previous sequence. This should cause the other
|
|
* end to send an ack. Don't queue or clone SKB, just
|
|
* send it.
|
|
*/
|
|
TCP_SKB_CB(skb)->seq = urgent ? tp->snd_una : tp->snd_una - 1;
|
|
TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq;
|
|
TCP_SKB_CB(skb)->when = tcp_time_stamp;
|
|
return tcp_transmit_skb(sk, skb);
|
|
}
|
|
|
|
int tcp_write_wakeup(struct sock *sk)
|
|
{
|
|
if (sk->sk_state != TCP_CLOSE) {
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
|
|
if ((skb = sk->sk_send_head) != NULL &&
|
|
before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)) {
|
|
int err;
|
|
unsigned int mss = tcp_current_mss(sk, 0);
|
|
unsigned int seg_size = tp->snd_una+tp->snd_wnd-TCP_SKB_CB(skb)->seq;
|
|
|
|
if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
|
|
tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
|
|
|
|
/* We are probing the opening of a window
|
|
* but the window size is != 0
|
|
* must have been a result SWS avoidance ( sender )
|
|
*/
|
|
if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
|
|
skb->len > mss) {
|
|
seg_size = min(seg_size, mss);
|
|
TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
|
|
if (tcp_fragment(sk, skb, seg_size, mss))
|
|
return -1;
|
|
} else if (!tcp_skb_pcount(skb))
|
|
tcp_set_skb_tso_segs(sk, skb, mss);
|
|
|
|
TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
|
|
TCP_SKB_CB(skb)->when = tcp_time_stamp;
|
|
err = tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC));
|
|
if (!err) {
|
|
update_send_head(sk, tp, skb);
|
|
}
|
|
return err;
|
|
} else {
|
|
if (tp->urg_mode &&
|
|
between(tp->snd_up, tp->snd_una+1, tp->snd_una+0xFFFF))
|
|
tcp_xmit_probe_skb(sk, TCPCB_URG);
|
|
return tcp_xmit_probe_skb(sk, 0);
|
|
}
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
/* A window probe timeout has occurred. If window is not closed send
|
|
* a partial packet else a zero probe.
|
|
*/
|
|
void tcp_send_probe0(struct sock *sk)
|
|
{
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int err;
|
|
|
|
err = tcp_write_wakeup(sk);
|
|
|
|
if (tp->packets_out || !sk->sk_send_head) {
|
|
/* Cancel probe timer, if it is not required. */
|
|
icsk->icsk_probes_out = 0;
|
|
icsk->icsk_backoff = 0;
|
|
return;
|
|
}
|
|
|
|
if (err <= 0) {
|
|
if (icsk->icsk_backoff < sysctl_tcp_retries2)
|
|
icsk->icsk_backoff++;
|
|
icsk->icsk_probes_out++;
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
|
|
min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
|
|
TCP_RTO_MAX);
|
|
} else {
|
|
/* If packet was not sent due to local congestion,
|
|
* do not backoff and do not remember icsk_probes_out.
|
|
* Let local senders to fight for local resources.
|
|
*
|
|
* Use accumulated backoff yet.
|
|
*/
|
|
if (!icsk->icsk_probes_out)
|
|
icsk->icsk_probes_out = 1;
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
|
|
min(icsk->icsk_rto << icsk->icsk_backoff,
|
|
TCP_RESOURCE_PROBE_INTERVAL),
|
|
TCP_RTO_MAX);
|
|
}
|
|
}
|
|
|
|
EXPORT_SYMBOL(tcp_connect);
|
|
EXPORT_SYMBOL(tcp_make_synack);
|
|
EXPORT_SYMBOL(tcp_simple_retransmit);
|
|
EXPORT_SYMBOL(tcp_sync_mss);
|