1#define _GNU_SOURCE
2#include <sys/socket.h>
3#include <limits.h>
4#include <errno.h>
5#include "syscall.h"
6
7int sendmmsg(int fd, struct mmsghdr *msgvec, unsigned int vlen, unsigned int flags)
8{
9#if LONG_MAX > INT_MAX
10	/* Can't use the syscall directly because the kernel has the wrong
11	 * idea for the types of msg_iovlen, msg_controllen, and cmsg_len,
12	 * and the cmsg blocks cannot be modified in-place. */
13	int i;
14	if (vlen > IOV_MAX) vlen = IOV_MAX; /* This matches the kernel. */
15	if (!vlen) return 0;
16	for (i=0; i<vlen; i++) {
17		/* As an unfortunate inconsistency, the sendmmsg API uses
18		 * unsigned int for the resulting msg_len, despite sendmsg
19		 * returning ssize_t. However Linux limits the total bytes
20		 * sent by sendmsg to INT_MAX, so the assignment is safe. */
21		ssize_t r = sendmsg(fd, &msgvec[i].msg_hdr, flags);
22		if (r < 0) goto error;
23		msgvec[i].msg_len = r;
24	}
25error:
26	return i ? i : -1;
27#else
28	return syscall_cp(SYS_sendmmsg, fd, msgvec, vlen, flags);
29#endif
30}
31