TCP: Add comments to (near) all functions in tcp_output.c v3
While looking for something else I spent some time adding one liner comments to the tcp_output.c functions that didn't have any. That makes the comments more consistent. I hope I documented everything right. No code changes. v2: Incorporated feedback from Ilpo. v3: Change style of one liner comments, add a few more comments. Signed-off-by: Andi Kleen <ak@linux.intel.com> Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Andi Kleen
David S. Miller
parent
40d4e3dfc2
commit
67edfef786
|
|
@ -59,6 +59,7 @@ int sysctl_tcp_base_mss __read_mostly = 512;
|
|||
/* By default, RFC2861 behavior. */
|
||||
int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
|
||||
|
||||
/* Account for new data that has been sent to the network. */
|
||||
static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
|
||||
{
|
||||
struct tcp_sock *tp = tcp_sk(sk);
|
||||
|
|
@ -142,6 +143,7 @@ static void tcp_cwnd_restart(struct sock *sk, struct dst_entry *dst)
|
|||
tp->snd_cwnd_used = 0;
|
||||
}
|
||||
|
||||
/* Congestion state accounting after a packet has been sent. */
|
||||
static void tcp_event_data_sent(struct tcp_sock *tp,
|
||||
struct sk_buff *skb, struct sock *sk)
|
||||
{
|
||||
|
|
@ -161,6 +163,7 @@ static void tcp_event_data_sent(struct tcp_sock *tp,
|
|||
icsk->icsk_ack.pingpong = 1;
|
||||
}
|
||||
|
||||
/* Account for an ACK we sent. */
|
||||
static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
|
||||
{
|
||||
tcp_dec_quickack_mode(sk, pkts);
|
||||
|
|
@ -276,6 +279,7 @@ static u16 tcp_select_window(struct sock *sk)
|
|||
return new_win;
|
||||
}
|
||||
|
||||
/* Packet ECN state for a SYN-ACK */
|
||||
static inline void TCP_ECN_send_synack(struct tcp_sock *tp, struct sk_buff *skb)
|
||||
{
|
||||
TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_CWR;
|
||||
|
|
@ -283,6 +287,7 @@ static inline void TCP_ECN_send_synack(struct tcp_sock *tp, struct sk_buff *skb)
|
|||
TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_ECE;
|
||||
}
|
||||
|
||||
/* Packet ECN state for a SYN. */
|
||||
static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb)
|
||||
{
|
||||
struct tcp_sock *tp = tcp_sk(sk);
|
||||
|
|
@ -301,6 +306,9 @@ TCP_ECN_make_synack(struct request_sock *req, struct tcphdr *th)
|
|||
th->ece = 1;
|
||||
}
|
||||
|
||||
/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
|
||||
* be sent.
|
||||
*/
|
||||
static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
|
||||
int tcp_header_len)
|
||||
{
|
||||
|
|
@ -362,7 +370,9 @@ struct tcp_out_options {
|
|||
__u32 tsval, tsecr; /* need to include OPTION_TS */
|
||||
};
|
||||
|
||||
/* Beware: Something in the Internet is very sensitive to the ordering of
|
||||
/* Write previously computed TCP options to the packet.
|
||||
*
|
||||
* Beware: Something in the Internet is very sensitive to the ordering of
|
||||
* TCP options, we learned this through the hard way, so be careful here.
|
||||
* Luckily we can at least blame others for their non-compliance but from
|
||||
* inter-operatibility perspective it seems that we're somewhat stuck with
|
||||
|
|
@ -445,6 +455,9 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
|
|||
}
|
||||
}
|
||||
|
||||
/* Compute TCP options for SYN packets. This is not the final
|
||||
* network wire format yet.
|
||||
*/
|
||||
static unsigned tcp_syn_options(struct sock *sk, struct sk_buff *skb,
|
||||
struct tcp_out_options *opts,
|
||||
struct tcp_md5sig_key **md5) {
|
||||
|
|
@ -493,6 +506,7 @@ static unsigned tcp_syn_options(struct sock *sk, struct sk_buff *skb,
|
|||
return size;
|
||||
}
|
||||
|
||||
/* Set up TCP options for SYN-ACKs. */
|
||||
static unsigned tcp_synack_options(struct sock *sk,
|
||||
struct request_sock *req,
|
||||
unsigned mss, struct sk_buff *skb,
|
||||
|
|
@ -541,6 +555,9 @@ static unsigned tcp_synack_options(struct sock *sk,
|
|||
return size;
|
||||
}
|
||||
|
||||
/* Compute TCP options for ESTABLISHED sockets. This is not the
|
||||
* final wire format yet.
|
||||
*/
|
||||
static unsigned tcp_established_options(struct sock *sk, struct sk_buff *skb,
|
||||
struct tcp_out_options *opts,
|
||||
struct tcp_md5sig_key **md5) {
|
||||
|
|
@ -705,7 +722,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
|
|||
return net_xmit_eval(err);
|
||||
}
|
||||
|
||||
/* This routine just queue's the buffer
|
||||
/* This routine just queues the buffer for sending.
|
||||
*
|
||||
* NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
|
||||
* otherwise socket can stall.
|
||||
|
|
@ -722,6 +739,7 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
|
|||
sk_mem_charge(sk, skb->truesize);
|
||||
}
|
||||
|
||||
/* Initialize TSO segments for a packet. */
|
||||
static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb,
|
||||
unsigned int mss_now)
|
||||
{
|
||||
|
|
@ -909,6 +927,7 @@ static void __pskb_trim_head(struct sk_buff *skb, int len)
|
|||
skb->len = skb->data_len;
|
||||
}
|
||||
|
||||
/* Remove acked data from a packet in the transmit queue. */
|
||||
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))
|
||||
|
|
@ -937,7 +956,7 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
|
|||
return 0;
|
||||
}
|
||||
|
||||
/* Not accounting for SACKs here. */
|
||||
/* Calculate MSS. Not accounting for SACKs here. */
|
||||
int tcp_mtu_to_mss(struct sock *sk, int pmtu)
|
||||
{
|
||||
struct tcp_sock *tp = tcp_sk(sk);
|
||||
|
|
@ -981,6 +1000,7 @@ int tcp_mss_to_mtu(struct sock *sk, int mss)
|
|||
return mtu;
|
||||
}
|
||||
|
||||
/* MTU probing init per socket */
|
||||
void tcp_mtup_init(struct sock *sk)
|
||||
{
|
||||
struct tcp_sock *tp = tcp_sk(sk);
|
||||
|
|
@ -1143,7 +1163,8 @@ static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp,
|
|||
return 0;
|
||||
}
|
||||
|
||||
/* This must be invoked the first time we consider transmitting
|
||||
/* Intialize TSO state of a skb.
|
||||
* This must be invoked the first time we consider transmitting
|
||||
* SKB onto the wire.
|
||||
*/
|
||||
static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb,
|
||||
|
|
@ -1158,6 +1179,7 @@ static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb,
|
|||
return tso_segs;
|
||||
}
|
||||
|
||||
/* Minshall's variant of the Nagle send check. */
|
||||
static inline int tcp_minshall_check(const struct tcp_sock *tp)
|
||||
{
|
||||
return after(tp->snd_sml, tp->snd_una) &&
|
||||
|
|
@ -1242,6 +1264,7 @@ static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb,
|
|||
return cwnd_quota;
|
||||
}
|
||||
|
||||
/* Test if sending is allowed right now. */
|
||||
int tcp_may_send_now(struct sock *sk)
|
||||
{
|
||||
struct tcp_sock *tp = tcp_sk(sk);
|
||||
|
|
@ -1378,6 +1401,10 @@ send_now:
|
|||
}
|
||||
|
||||
/* Create a new MTU probe if we are ready.
|
||||
* MTU probe is regularly attempting to increase the path MTU by
|
||||
* deliberately sending larger packets. This discovers routing
|
||||
* changes resulting in larger path MTUs.
|
||||
*
|
||||
* Returns 0 if we should wait to probe (no cwnd available),
|
||||
* 1 if a probe was sent,
|
||||
* -1 otherwise
|
||||
|
|
@ -1790,6 +1817,7 @@ static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
|
|||
sk_wmem_free_skb(sk, next_skb);
|
||||
}
|
||||
|
||||
/* Check if coalescing SKBs is legal. */
|
||||
static int tcp_can_collapse(struct sock *sk, struct sk_buff *skb)
|
||||
{
|
||||
if (tcp_skb_pcount(skb) > 1)
|
||||
|
|
@ -1808,6 +1836,9 @@ static int tcp_can_collapse(struct sock *sk, struct sk_buff *skb)
|
|||
return 1;
|
||||
}
|
||||
|
||||
/* Collapse packets in the retransmit queue to make to create
|
||||
* less packets on the wire. This is only done on retransmission.
|
||||
*/
|
||||
static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
|
||||
int space)
|
||||
{
|
||||
|
|
@ -1957,6 +1988,9 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
|
|||
return err;
|
||||
}
|
||||
|
||||
/* Check if we forward retransmits are possible in the current
|
||||
* window/congestion state.
|
||||
*/
|
||||
static int tcp_can_forward_retransmit(struct sock *sk)
|
||||
{
|
||||
const struct inet_connection_sock *icsk = inet_csk(sk);
|
||||
|
|
@ -2145,7 +2179,8 @@ void tcp_send_active_reset(struct sock *sk, gfp_t priority)
|
|||
TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
|
||||
}
|
||||
|
||||
/* WARNING: This routine must only be called when we have already sent
|
||||
/* Send a crossed SYN-ACK during socket establishment.
|
||||
* 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.
|
||||
|
|
@ -2180,9 +2215,7 @@ int tcp_send_synack(struct sock *sk)
|
|||
return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
|
||||
}
|
||||
|
||||
/*
|
||||
* Prepare a SYN-ACK.
|
||||
*/
|
||||
/* Prepare a SYN-ACK. */
|
||||
struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
|
||||
struct request_sock *req)
|
||||
{
|
||||
|
|
@ -2269,9 +2302,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
|
|||
return skb;
|
||||
}
|
||||
|
||||
/*
|
||||
* Do all connect socket setups that can be done AF independent.
|
||||
*/
|
||||
/* Do all connect socket setups that can be done AF independent. */
|
||||
static void tcp_connect_init(struct sock *sk)
|
||||
{
|
||||
struct dst_entry *dst = __sk_dst_get(sk);
|
||||
|
|
@ -2330,9 +2361,7 @@ static void tcp_connect_init(struct sock *sk)
|
|||
tcp_clear_retrans(tp);
|
||||
}
|
||||
|
||||
/*
|
||||
* Build a SYN and send it off.
|
||||
*/
|
||||
/* Build a SYN and send it off. */
|
||||
int tcp_connect(struct sock *sk)
|
||||
{
|
||||
struct tcp_sock *tp = tcp_sk(sk);
|
||||
|
|
@ -2493,6 +2522,7 @@ static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
|
|||
return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
|
||||
}
|
||||
|
||||
/* Initiate keepalive or window probe from timer. */
|
||||
int tcp_write_wakeup(struct sock *sk)
|
||||
{
|
||||
struct tcp_sock *tp = tcp_sk(sk);
|
||||
|
|
|
|||
Loading…
Reference in a new issue