| Message ID | 1657532838-20200-1-git-send-email-liyonglong@chinatelecom.cn (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 536a6c8e05f95e3d1118c40ae8b3022ee2d05d52 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v4] tcp: make retransmitted SKB fit into the send window | expand |
On Mon, Jul 11, 2022 at 12:06 PM Yonglong Li <liyonglong@chinatelecom.cn> wrote: > > current code of __tcp_retransmit_skb only check TCP_SKB_CB(skb)->seq > in send window, and TCP_SKB_CB(skb)->seq_end maybe out of send window. > If receiver has shrunk his window, and skb is out of new window, it > should retransmit a smaller portion of the payload. > > test packetdrill script: > 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 > +0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR) > +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 > > +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress) > +0 > S 0:0(0) win 65535 <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8> > +.05 < S. 0:0(0) ack 1 win 6000 <mss 1000,nop,nop,sackOK> > +0 > . 1:1(0) ack 1 > > +0 write(3, ..., 10000) = 10000 > > +0 > . 1:2001(2000) ack 1 win 65535 > +0 > . 2001:4001(2000) ack 1 win 65535 > +0 > . 4001:6001(2000) ack 1 win 65535 > > +.05 < . 1:1(0) ack 4001 win 1001 > > and tcpdump show: > 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 1:2001, ack 1, win 65535, length 2000 > 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 2001:4001, ack 1, win 65535, length 2000 > 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000 > 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000 > 192.0.2.1.8080 > 192.168.226.67.55: Flags [.], ack 4001, win 1001, length 0 > 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000 > 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000 > > when cient retract window to 1001, send window is [4001,5002], > but TLP send 5001-6001 packet which is out of send window. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Yonglong Li <liyonglong@chinatelecom.cn> Signed-off-by: Eric Dumazet <edumazet@google.com> Thanks !
Hello: This patch was applied to netdev/net-next.git (master) by Jakub Kicinski <kuba@kernel.org>: On Mon, 11 Jul 2022 17:47:18 +0800 you wrote: > current code of __tcp_retransmit_skb only check TCP_SKB_CB(skb)->seq > in send window, and TCP_SKB_CB(skb)->seq_end maybe out of send window. > If receiver has shrunk his window, and skb is out of new window, it > should retransmit a smaller portion of the payload. > > test packetdrill script: > 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 > +0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR) > +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 > > [...] Here is the summary with links: - [v4] tcp: make retransmitted SKB fit into the send window https://git.kernel.org/netdev/net-next/c/536a6c8e05f9 You are awesome, thank you!
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 18c913a..d1ca3df 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -3144,7 +3144,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) struct tcp_sock *tp = tcp_sk(sk); unsigned int cur_mss; int diff, len, err; - + int avail_wnd; /* Inconclusive MTU probe */ if (icsk->icsk_mtup.probe_size) @@ -3166,17 +3166,25 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) return -EHOSTUNREACH; /* Routing failure or similar. */ cur_mss = tcp_current_mss(sk); + avail_wnd = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; /* 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. + * our retransmit of one segment serves as a zero window probe. */ - if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) && - TCP_SKB_CB(skb)->seq != tp->snd_una) - return -EAGAIN; + if (avail_wnd <= 0) { + if (TCP_SKB_CB(skb)->seq != tp->snd_una) + return -EAGAIN; + avail_wnd = cur_mss; + } len = cur_mss * segs; + if (len > avail_wnd) { + len = rounddown(avail_wnd, cur_mss); + if (!len) + len = avail_wnd; + } if (skb->len > len) { if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len, cur_mss, GFP_ATOMIC)) @@ -3190,8 +3198,9 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) diff -= tcp_skb_pcount(skb); if (diff) tcp_adjust_pcount(sk, skb, diff); - if (skb->len < cur_mss) - tcp_retrans_try_collapse(sk, skb, cur_mss); + avail_wnd = min_t(int, avail_wnd, cur_mss); + if (skb->len < avail_wnd) + tcp_retrans_try_collapse(sk, skb, avail_wnd); } /* RFC3168, section 6.1.1.1. ECN fallback */
current code of __tcp_retransmit_skb only check TCP_SKB_CB(skb)->seq in send window, and TCP_SKB_CB(skb)->seq_end maybe out of send window. If receiver has shrunk his window, and skb is out of new window, it should retransmit a smaller portion of the payload. test packetdrill script: 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR) +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress) +0 > S 0:0(0) win 65535 <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8> +.05 < S. 0:0(0) ack 1 win 6000 <mss 1000,nop,nop,sackOK> +0 > . 1:1(0) ack 1 +0 write(3, ..., 10000) = 10000 +0 > . 1:2001(2000) ack 1 win 65535 +0 > . 2001:4001(2000) ack 1 win 65535 +0 > . 4001:6001(2000) ack 1 win 65535 +.05 < . 1:1(0) ack 4001 win 1001 and tcpdump show: 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 1:2001, ack 1, win 65535, length 2000 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 2001:4001, ack 1, win 65535, length 2000 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000 192.0.2.1.8080 > 192.168.226.67.55: Flags [.], ack 4001, win 1001, length 0 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000 when cient retract window to 1001, send window is [4001,5002], but TLP send 5001-6001 packet which is out of send window. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Yonglong Li <liyonglong@chinatelecom.cn> --- net/ipv4/tcp_output.c | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-)