github.com/afumu/libc@v0.0.6/musl/src/network/sendmmsg.c (about)

     1  #define _GNU_SOURCE
     2  #include <sys/socket.h>
     3  #include <limits.h>
     4  #include <errno.h>
     5  #include "syscall.h"
     6  
     7  int 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  	}
    25  error:
    26  	return i ? i : -1;
    27  #else
    28  	return syscall_cp(SYS_sendmmsg, fd, msgvec, vlen, flags);
    29  #endif
    30  }