> I just want to be sure that the buffer and nread given in
> uv_udp_recv_cb will just point to a **single** received UDP datagram
> (as always). I assume this is true, otherwise it would be a super
> breaking change since the application should do parsing to separate
> different messages received into two separate UDP datagrams.
Ok, by looking at the code in depth it seems that, indeed, nothing
changes and, no matter recvmmsg is used, a recv_cb() is called for
each received datagram:
In src/unix/udp.c:
--------------------------------
#if HAVE_MMSG
static int uv__udp_recvmmsg(uv_udp_t* handle, uv_buf_t* buf) {
struct sockaddr_in6 peers[UV__MMSG_MAXWIDTH];
struct iovec iov[UV__MMSG_MAXWIDTH];
struct uv__mmsghdr msgs[UV__MMSG_MAXWIDTH];
ssize_t nread;
uv_buf_t chunk_buf;
size_t chunks;
int flags;
size_t k;
/* prepare structures for recvmmsg */
chunks = buf->len / UV__UDP_DGRAM_MAXSIZE;
if (chunks > ARRAY_SIZE(iov))
chunks = ARRAY_SIZE(iov);
for (k = 0; k < chunks; ++k) {
iov[k].iov_base = buf->base + k * UV__UDP_DGRAM_MAXSIZE;
iov[k].iov_len = UV__UDP_DGRAM_MAXSIZE;
msgs[k].msg_hdr.msg_iov = iov + k;
msgs[k].msg_hdr.msg_iovlen = 1;
msgs[k].msg_hdr.msg_name = peers + k;
msgs[k].msg_hdr.msg_namelen = sizeof(peers[0]);
}
do
nread = uv__recvmmsg(handle->io_watcher.fd, msgs, chunks, 0, NULL);
while (nread == -1 && errno == EINTR);
if (nread < 1) {
if (nread == 0 || errno == EAGAIN || errno == EWOULDBLOCK)
handle->recv_cb(handle, 0, buf, NULL, 0);
else
handle->recv_cb(handle, UV__ERR(errno), buf, NULL, 0);
} else {
/* count to zero, so the buffer base comes last */
for (k = nread; k > 0 && handle->recv_cb != NULL;) {
k--;
flags = 0;
if (msgs[k].msg_hdr.msg_flags & MSG_TRUNC)
flags |= UV_UDP_PARTIAL;
if (k != 0)
flags |= UV_UDP_MMSG_CHUNK;
chunk_buf = uv_buf_init(iov[k].iov_base, iov[k].iov_len);
handle->recv_cb(handle,
msgs[k].msg_len,
&chunk_buf,
msgs[k].msg_hdr.msg_name,
flags);
}
}
return nread;
}
#endif
-----------------------
--
Iñaki Baz Castillo
<[email protected]>
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