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[PULL,08/52] gdbstub: set listen backlog to 1

Message ID 0b49921d791e56830e9f93bea4de20208244fff2.1465112552.git.mjt@msgid.tls.msk.ru
State New
Headers show

Commit Message

Michael Tokarev June 5, 2016, 7:42 a.m. UTC 
From: Peter Wu <peter@lekensteyn.nl>

Avoid possible connection drops on Linux (when tcp_syncookies is
disabled) or fallbacks to SYN cookies with the following kernel warning:

    TCP: request_sock_TCP: Possible SYN flooding on port 1234. Sending cookies.  Check SNMP counters.

Since Linux 4.4 (ef547f2ac16b "tcp: remove max_qlen_log"), a backlog of
zero is really treated as the "queue length for completely established
sockets waiting to be accepted" (listen(2)). This is apparently a valid
interpretation of an "implementation-defined minimum value" for a
backlog value of 0 (listen(3p)). Previous kernels would use 8 as
minimum value, but that is no longer the case.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
---
 gdbstub.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/gdbstub.c b/gdbstub.c
index b9e3710..ffcad0e 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -1629,7 +1629,7 @@  static int gdbserver_open(int port)
         close(fd);
         return -1;
     }
-    ret = listen(fd, 0);
+    ret = listen(fd, 1);
     if (ret < 0) {
         perror("listen");
         close(fd);