src/network/sendmmsg.c

   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 }