SO_REUSEPORT on linux

问题:

I want to know if SO_REUSEPORT option is enabled in LINUX 2.6 or not ??

If I try to use it and compile my code I get following error

01.c:72: error: `SO_REUSEPORT' undeclared (first use in this function)
01.c:72: error: (Each undeclared identifier is reported only once
01.c:72: error: for each function it appears in.)

Using the above option I guess I can bind two different sockets to same IPADRESS and PORT NUMBER

回答1:

this options was done in kernel 3.9, see this git commit

http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c617f398edd4db2b8567a28e899a88f8f574798d

回答2:

From /usr/include/asm-generic/socket.h:

/* For setsockopt(2) */
#define SOL_SOCKET      1

#define SO_DEBUG        1
#define SO_REUSEADDR    2
#define SO_TYPE         3
#define SO_ERROR        4
#define SO_DONTROUTE    5
#define SO_BROADCAST    6
#define SO_SNDBUF       7
#define SO_RCVBUF       8
#define SO_SNDBUFFORCE  32
#define SO_RCVBUFFORCE  33
#define SO_KEEPALIVE    9
#define SO_OOBINLINE    10
#define SO_NO_CHECK     11
#define SO_PRIORITY     12
#define SO_LINGER       13
#define SO_BSDCOMPAT    14
/* To add :#define SO_REUSEPORT 15 */

Hmmm. Looks like it's undefined or on the last stages of being depreciated.

Here's what a post on KernelTrap says:

On Linux, SO_REUSEADDR provide most of what SO_REUSEPORT provides on BSD.

In any case, there is absolutely no point in creating multiple TCP listeners.
Multiple threads can accept() on the same listener - at the same time.
--
Rémi Denis-Courmont
http://www.remlab.net/

回答3:

Try this:

#ifdefined (SO_REUSEPORT)
... set this option
#endif

Some platforms (OS/X for one) need this to be set if you're e.g. binding multiple UDP listeners to one port.

回答4:

SO_REUSEPORT was backported to the RHEL6.5 kernel 2.6.32.

回答5:

It was added during the 3.9 cycle in a series of patches by Tom Herbert, as you can see here, in order to better support multithreaded web servers.

The patch itself can be found here if you want to integrate SO_REUSEPORT into an older kernel version.

And yes, you can use SO_REUSEPORT to bind a socket to the same address and port as another connection, as long as the initial connection also uses SO_REUSEPORT (and any other connections sharing the source address and port). This is done to prevent port hijacking by rogue applications.