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tcp: dump and restore window parameters

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We found that sometimes a restored tcp socket doesn't work.

A reason of this bug is incorrect window parameters and in this case
tcp_acceptable_seq() returns tcp_wnd_end(tp) instead of tp->snd_nxt. The
other side drops packets with this seq, because seq is less than
tp->rcv_nxt ( tcp_sequence() ).

We need to restore window parameters to avoid such side effects.

https://github.com/xemul/criu/issues/168
Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
This commit is contained in:
Andrew Vagin 2016-07-13 05:16:00 +03:00 • committed by Pavel Emelyanov
parent f3b730d0e2
commit 7d95face06
2 changed files with 63 additions and 0 deletions
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57
criu/sk-tcp.c
View file

@ -319,6 +319,34 @@ err_sopt:
return -1;
}
static int tcp_get_window(int sk, TcpStreamEntry *tse)
{
struct tcp_repair_window opt;
socklen_t optlen = sizeof(opt);
if (!kdat.has_tcp_window)
return 0;
if (getsockopt(sk, SOL_TCP,
TCP_REPAIR_WINDOW, &opt, &optlen)) {
pr_perror("Unable to get window properties");
return -1;
}
tse->has_snd_wl1 = true;
tse->has_snd_wnd = true;
tse->has_max_window = true;
tse->has_rcv_wnd = true;
tse->has_rcv_wup = true;
tse->snd_wl1 = opt.snd_wl1;
tse->snd_wnd = opt.snd_wnd;
tse->max_window = opt.max_window;
tse->rcv_wnd = opt.rcv_wnd;
tse->rcv_wup = opt.rcv_wup;
return 0;
}
static int dump_tcp_conn_state(struct inet_sk_desc *sk)
{
int ret, aux;
@ -364,6 +392,9 @@ static int dump_tcp_conn_state(struct inet_sk_desc *sk)
if (ret < 0)
goto err_opt;
if (tcp_get_window(sk->rfd, &tse))
goto err_opt;
/*
* TCP socket options
*/
@ -624,6 +655,29 @@ static int restore_tcp_opts(int sk, TcpStreamEntry *tse)
return 0;
}
static int restore_tcp_window(int sk, TcpStreamEntry *tse)
{
struct tcp_repair_window opt = {
.snd_wl1 = tse->snd_wl1,
.snd_wnd = tse->snd_wnd,
.max_window = tse->max_window,
.rcv_wnd = tse->rcv_wnd,
.rcv_wup = tse->rcv_wup,
};
if (!kdat.has_tcp_window || !tse->has_snd_wnd) {
pr_warn_once("Window parameters are not restored\n");
return 0;
}
if (setsockopt(sk, SOL_TCP, TCP_REPAIR_WINDOW, &opt, sizeof(opt))) {
pr_perror("Unable to set window parameters");
return -1;
}
return 0;
}
static int restore_tcp_conn_state(int sk, struct inet_sk_info *ii)
{
int aux;
@ -657,6 +711,9 @@ static int restore_tcp_conn_state(int sk, struct inet_sk_info *ii)
if (restore_tcp_queues(sk, tse, img))
goto err_c;
if (restore_tcp_window(sk, tse))
goto err_c;
if (tse->has_nodelay && tse->nodelay) {
aux = 1;
if (restore_opt(sk, SOL_TCP, TCP_NODELAY, &aux))

6
images/tcp-stream.proto
View file

@ -18,4 +18,10 @@ message tcp_stream_entry {
optional bool nodelay = 11;
optional uint32 unsq_len = 12; /* unsent data in the send queue */
optional uint32 snd_wl1 = 13;
optional uint32 snd_wnd = 14;
optional uint32 max_window = 15;
optional uint32 rcv_wnd = 16;
optional uint32 rcv_wup = 17;
}