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authorStefan Baranoff <sbaranoff@gmail.com>2018-07-10 17:25:20 -0400
committerDavid S. Miller <davem@davemloft.net>2018-07-12 14:33:45 -0700
commit21684dc46c598e477707487c009f9773f7c0382d (patch)
treee32dc7d79947a09fc058069de742ea476db4cc83 /net/ipv4/tcp_ipv4.c
parent83fe6b8709f65bc505b10235bd82ece12c4c5099 (diff)
tcp: fix sequence numbers for repaired sockets re-using TIME-WAIT sockets
This patch fixes a bug where the sequence numbers of a socket created using TCP repair functionality are lower than set after connect is called. This occurs when the repair socket overlaps with a TIME-WAIT socket and triggers the re-use code. The amount lower is equal to the number of times that a particular IP/port set is re-used and then put back into TIME-WAIT. Re-using the first time the sequence number is 1 lower, closing that socket and then re-opening (with repair) a new socket with the same addresses/ports puts the sequence number 2 lower than set via setsockopt. The third time is 3 lower, etc. I have not tested what the limit of this acrewal is, if any. The fix is, if a socket is in repair mode, to respect the already set sequence number and timestamp when it would have already re-used the TIME-WAIT socket. Signed-off-by: Stefan Baranoff <sbaranoff@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_ipv4.c')
-rw-r--r--net/ipv4/tcp_ipv4.c23
1 files changed, 18 insertions, 5 deletions
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index bea17f1e8302..3b2711e33e4c 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -156,11 +156,24 @@ int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
*/
if (tcptw->tw_ts_recent_stamp &&
(!twp || (reuse && get_seconds() - tcptw->tw_ts_recent_stamp > 1))) {
- tp->write_seq = tcptw->tw_snd_nxt + 65535 + 2;
- if (tp->write_seq == 0)
- tp->write_seq = 1;
- tp->rx_opt.ts_recent = tcptw->tw_ts_recent;
- tp->rx_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
+ /* In case of repair and re-using TIME-WAIT sockets we still
+ * want to be sure that it is safe as above but honor the
+ * sequence numbers and time stamps set as part of the repair
+ * process.
+ *
+ * Without this check re-using a TIME-WAIT socket with TCP
+ * repair would accumulate a -1 on the repair assigned
+ * sequence number. The first time it is reused the sequence
+ * is -1, the second time -2, etc. This fixes that issue
+ * without appearing to create any others.
+ */
+ if (likely(!tp->repair)) {
+ tp->write_seq = tcptw->tw_snd_nxt + 65535 + 2;
+ if (tp->write_seq == 0)
+ tp->write_seq = 1;
+ tp->rx_opt.ts_recent = tcptw->tw_ts_recent;
+ tp->rx_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
+ }
sock_hold(sktw);
return 1;
}