Update SOMAXCONN value from Linux 5.4.

Linux 5.4 changes the SOMAXCONN value from 128 to 4096 (this isn't in
a uapi header; various constants related to the kernel/userspace
interface, including this one, are in the non-uapi linux/socket.h
header).

This patch increases the value in glibc.  As I understand it, it is
safe to use a higher value even with older kernels (the kernel will
simply adjust the value passed to listen to be no more than the value
supported in the kernel), and SOMAXCONN is actually only a default for
a sysctl value in the kernel that can be changed at runtime.  So I
think updating the value in glibc is a reasonable and safe thing to
do.

Tested for x86_64.

diff --git a/sysdeps/unix/sysv/linux/bits/socket.h b/sysdeps/unix/sysv/linux/bits/socket.h
index 3e88d66328a1a9574ed9efdfda4718ef07c1bb4b..7537a7e86b74be441dc283036cafd9369bc912cf 100644 (file)
--- a/sysdeps/unix/sysv/linux/bits/socket.h
+++ b/sysdeps/unix/sysv/linux/bits/socket.h
@@ -169,7 +169,7 @@ typedef __socklen_t socklen_t;
 #define SOL_XDP                283
 
 /* Maximum queue length specifiable by listen.  */
-#define SOMAXCONN      128
+#define SOMAXCONN      4096
 
 /* Get the definition of the macro to define the common sockaddr members.  */
 #include <bits/sockaddr.h>