#define _GNU_SOURCE
#include <sys/socket.h>
#include <limits.h>
#include <errno.h>
#include "syscall.h"

int sendmmsg(int fd,
             struct mmsghdr* msgvec,
             unsigned int vlen,
             unsigned int flags) {
#if LONG_MAX > INT_MAX
  /* Can't use the syscall directly because the kernel has the wrong
   * idea for the types of msg_iovlen, msg_controllen, and cmsg_len,
   * and the cmsg blocks cannot be modified in-place. */
  int i;
  if (vlen > IOV_MAX)
    vlen = IOV_MAX; /* This matches the kernel. */
  if (!vlen)
    return 0;
  for (i = 0; i < vlen; i++) {
    /* As an unfortunate inconsistency, the sendmmsg API uses
     * unsigned int for the resulting msg_len, despite sendmsg
     * returning ssize_t. However Linux limits the total bytes
     * sent by sendmsg to INT_MAX, so the assignment is safe. */
    ssize_t r = sendmsg(fd, &msgvec[i].msg_hdr, flags);
    if (r < 0)
      goto error;
    msgvec[i].msg_len = r;
  }
error:
  return i ? i : -1;
#else
  return syscall_cp(SYS_sendmmsg, fd, msgvec, vlen, flags);
#endif
}