Commit ec342325 authored Nov 15, 2012 by Andrew Vagin Committed by David S. Miller Nov 15, 2012

tcp: fix retransmission in repair mode



Currently if a socket was repaired with a few packet in a write queue,
a kernel bug may be triggered:

kernel BUG at net/ipv4/tcp_output.c:2330!
RIP: 0010:[<ffffffff8155784f>] tcp_retransmit_skb+0x5ff/0x610

According to the initial realization v3.4-rc2-963-gc0e88ff,
all skb-s should look like already posted. This patch fixes code
according with this sentence.

Here are three points, which were not done in the initial patch:
1. A tcp send head should not be changed
2. Initialize TSO state of a skb
3. Reset the retransmission time

This patch moves logic from tcp_sendmsg to tcp_write_xmit. A packet
passes the ussual way, but isn't sent to network. This patch solves
all described problems and handles tcp_sendpages.

Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 0da9a0c2

net/ipv4/tcp.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1212,7 +1212,7 @@ new_segment:
		wait_for_sndbuf:
		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
		wait_for_memory:
		if (copied && likely(!tp->repair))
		if (copied)
		tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH);

		if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
		@@ -1223,7 +1223,7 @@ wait_for_memory:
		}

		out:
		if (copied && likely(!tp->repair))
		if (copied)
		tcp_push(sk, flags, mss_now, tp->nonagle);
		release_sock(sk);
		return copied + copied_syn;

net/ipv4/tcp_output.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -1986,6 +1986,9 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
		tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
		BUG_ON(!tso_segs);

		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE)
		goto repair; /* Skip network transmission */

		cwnd_quota = tcp_cwnd_test(tp, skb);
		if (!cwnd_quota)
		break;
		@@ -2026,6 +2029,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
		break;

		repair:
		/* Advance the send_head. This one is sent out.
		* This call will increment packets_out.
		*/

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