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authorEric Dumazet <edumazet@google.com>2019-10-30 09:36:20 -0700
committerDavid S. Miller <davem@davemloft.net>2019-10-31 14:01:40 -0700
commit19f92a030ca6d772ab44b22ee6a01378a8cb32d4 (patch)
tree29ef4d4bfa78c7b0e21b4adeb0ffc27691021e75 /Documentation
parent6d6f0383b697f004c65823c2b64240912f18515d (diff)
net: increase SOMAXCONN to 4096
SOMAXCONN is /proc/sys/net/core/somaxconn default value. It has been defined as 128 more than 20 years ago. Since it caps the listen() backlog values, the very small value has caused numerous problems over the years, and many people had to raise it on their hosts after beeing hit by problems. Google has been using 1024 for at least 15 years, and we increased this to 4096 after TCP listener rework has been completed, more than 4 years ago. We got no complain of this change breaking any legacy application. Many applications indeed setup a TCP listener with listen(fd, -1); meaning they let the system select the backlog. Raising SOMAXCONN lowers chance of the port being unavailable under even small SYNFLOOD attack, and reduces possibilities of side channel vulnerabilities. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Willy Tarreau <w@1wt.eu> Cc: Yue Cao <ycao009@ucr.edu> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/networking/ip-sysctl.txt4
1 files changed, 2 insertions, 2 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 49e95f438ed7..0e6653471c0e 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -207,8 +207,8 @@ TCP variables:
somaxconn - INTEGER
Limit of socket listen() backlog, known in userspace as SOMAXCONN.
- Defaults to 128. See also tcp_max_syn_backlog for additional tuning
- for TCP sockets.
+ Defaults to 4096. (Was 128 before linux-5.4)
+ See also tcp_max_syn_backlog for additional tuning for TCP sockets.
tcp_abort_on_overflow - BOOLEAN
If listening service is too slow to accept new connections,