Does FreeBSD have sendmmsg or recvmmsg system calls?

[Jilles Tjoelker]

On Tue, Jan 19, 2016 at 01:58:27PM +0200, Boris Astardzhiev wrote:
> I removed the pthread_testcancel() calls and cut the interposing
> stuff from my patch as suggested. I extended the send/recv(2) manpages
> regarding
> the mm calls. Comments and suggestions?

> [snip]
> diff --git a/lib/libc/sys/Symbol.map b/lib/libc/sys/Symbol.map
> index 7b3257c..724e1b4 100644
> --- a/lib/libc/sys/Symbol.map
> +++ b/lib/libc/sys/Symbol.map
> @@ -399,6 +399,8 @@ FBSD_1.4 {
>  	utimensat;
>  	numa_setaffinity;
>  	numa_getaffinity;
> +	sendmmsg;
> +	recvmmsg;
>  };

OK.

>  
>  FBSDprivate_1.0 {
> @@ -1051,4 +1053,6 @@ FBSDprivate_1.0 {
>  	gssd_syscall;
>  	__libc_interposing_slot;
>  	__libc_sigwait;
> +	_sendmmsg;
> +	_recvmmsg;
>  };

The _ versions need not be exported. Not exporting reduces code size and
improves performance.

> diff --git a/lib/libc/sys/recv.2 b/lib/libc/sys/recv.2
> index 326e7ff..81a0201 100644
> --- a/lib/libc/sys/recv.2
> +++ b/lib/libc/sys/recv.2
> [snip]

I think the recv.2 and send.2 man pages are long enough as they are, and
separate recvmmsg.3 and sendmmsg.3 pages will be clearer. This is also
because recvmmsg/sendmmsg can be ignored when performance is good enough
without them. This differs from what Konstantin thinks.

> diff --git a/lib/libc/sys/recvmmsg.c b/lib/libc/sys/recvmmsg.c
> new file mode 100644
> index 0000000..6b5158a
> --- /dev/null
> +++ b/lib/libc/sys/recvmmsg.c
> @@ -0,0 +1,72 @@
> [snip]
> +int
> +recvmmsg(int s, struct mmsghdr *msgvec, unsigned int vlen, int flags)
> +{

The Linux version has an additional parameter struct timespec *timeout
(but only for recvmmsg, not for sendmmsg). Note that implementing this
in a Linux-compatible manner has low overhead, since Linux only checks
it between packets and never interrupts a wait because of this timeout
(source: http://man7.org/linux/man-pages/man2/recvmmsg.2.html ).

> [snip]

-- 
Jilles Tjoelker