fix sendmmsg emulation return value for zero-length vector

this case is not even documented, but the kernel returns 0 here and it
makes sense to be consistent.

diff --git a/src/network/sendmmsg.c b/src/network/sendmmsg.c
index ff9f86187238d71df0321460c186cd36f1797934..eeae1d0a5822503f5c572a46e3d3696f6c95b1b9 100644 (file)
--- a/src/network/sendmmsg.c
+++ b/src/network/sendmmsg.c
@@ -12,6 +12,7 @@ int sendmmsg(int fd, struct mmsghdr *msgvec, unsigned int vlen, unsigned int fla
         * 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