dccp: Allow to distinguish original and retransmitted packets
This patch allows the sender to distinguish original and retransmitted packets, which is in particular needed for the retransmission of DCCP-Requests: * the first Request uses ISS (generated in net/dccp/ip*.c), and sets GSS = ISS; * all retransmitted Requests use GSS' = GSS + 1, so that the n-th retransmitted Request has sequence number ISS + n (mod 48). To add generic support, the patch reorganises existing code so that: * icsk_retransmits == 0 for the original packet and * icsk_retransmits = n > 0 for the n-th retransmitted packet at the time dccp_transmit_skb() is called, via dccp_retransmit_skb(). Thanks to Wei Yongjun for pointing this problem out. Further changes: ---------------- * removed the `skb' argument from dccp_retransmit_skb(), since sk_send_head is used for all retransmissions (the exception is client-Acks in PARTOPEN state, but these do not use sk_send_head); * since sk_send_head always contains the original skb (via dccp_entail()), skb_cloned() never evaluated to true and thus pskb_copy() was never used. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
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@ -226,7 +226,7 @@ static inline void dccp_csum_outgoing(struct sk_buff *skb)
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extern void dccp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb);
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extern int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb);
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extern int dccp_retransmit_skb(struct sock *sk);
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extern void dccp_send_ack(struct sock *sk);
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extern void dccp_reqsk_send_ack(struct sk_buff *sk, struct request_sock *rsk);
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@ -284,14 +284,26 @@ void dccp_write_xmit(struct sock *sk, int block)
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}
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}
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int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
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/**
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* dccp_retransmit_skb - Retransmit Request, Close, or CloseReq packets
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* There are only four retransmittable packet types in DCCP:
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* - Request in client-REQUEST state (sec. 8.1.1),
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* - CloseReq in server-CLOSEREQ state (sec. 8.3),
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* - Close in node-CLOSING state (sec. 8.3),
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* - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()).
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* This function expects sk->sk_send_head to contain the original skb.
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*/
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int dccp_retransmit_skb(struct sock *sk)
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{
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WARN_ON(sk->sk_send_head == NULL);
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if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
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return -EHOSTUNREACH; /* Routing failure or similar. */
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return dccp_transmit_skb(sk, (skb_cloned(skb) ?
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pskb_copy(skb, GFP_ATOMIC):
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skb_clone(skb, GFP_ATOMIC)));
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/* this count is used to distinguish original and retransmitted skb */
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inet_csk(sk)->icsk_retransmits++;
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return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC));
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}
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struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
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@ -98,22 +98,12 @@ static void dccp_retransmit_timer(struct sock *sk)
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goto backoff;
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}
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/*
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* sk->sk_send_head has to have one skb with
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* DCCP_SKB_CB(skb)->dccpd_type set to one of the retransmittable DCCP
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* packet types. The only packets eligible for retransmission are:
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* -- Requests in client-REQUEST state (sec. 8.1.1)
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* -- Acks in client-PARTOPEN state (sec. 8.1.5)
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* -- CloseReq in server-CLOSEREQ state (sec. 8.3)
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* -- Close in node-CLOSING state (sec. 8.3) */
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WARN_ON(sk->sk_send_head == NULL);
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/*
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* More than than 4MSL (8 minutes) has passed, a RESET(aborted) was
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* sent, no need to retransmit, this sock is dead.
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*/
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if (dccp_write_timeout(sk))
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goto out;
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return;
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/*
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* We want to know the number of packets retransmitted, not the
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@ -122,30 +112,28 @@ static void dccp_retransmit_timer(struct sock *sk)
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if (icsk->icsk_retransmits == 0)
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DCCP_INC_STATS_BH(DCCP_MIB_TIMEOUTS);
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if (dccp_retransmit_skb(sk, sk->sk_send_head) < 0) {
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if (dccp_retransmit_skb(sk) != 0) {
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/*
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* Retransmission failed because of local congestion,
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* do not backoff.
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*/
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if (icsk->icsk_retransmits == 0)
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if (--icsk->icsk_retransmits == 0)
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icsk->icsk_retransmits = 1;
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inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
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min(icsk->icsk_rto,
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TCP_RESOURCE_PROBE_INTERVAL),
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DCCP_RTO_MAX);
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goto out;
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return;
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}
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backoff:
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icsk->icsk_backoff++;
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icsk->icsk_retransmits++;
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icsk->icsk_rto = min(icsk->icsk_rto << 1, DCCP_RTO_MAX);
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inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto,
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DCCP_RTO_MAX);
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if (icsk->icsk_retransmits > sysctl_dccp_retries1)
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__sk_dst_reset(sk);
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out:;
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}
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static void dccp_write_timer(unsigned long data)
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