casaroli commented on code in PR #20702:
URL: https://github.com/apache/nuttx/pull/20702#discussion_r4415757793
##########
net/inet/inet_sockif.c:
##########
@@ -1839,20 +1839,60 @@ static ssize_t inet_sendto(FAR struct socket *psock,
FAR const void *buf,
static ssize_t inet_sendmsg(FAR struct socket *psock,
FAR const struct msghdr *msg, int flags)
{
- FAR void *buf = msg->msg_iov->iov_base;
- size_t len = msg->msg_iov->iov_len;
+ FAR void *buf;
+ size_t len;
FAR const struct sockaddr *to = msg->msg_name;
socklen_t tolen = msg->msg_namelen;
FAR const struct iovec *iov;
FAR const struct iovec *end;
int ret;
+ if (msg->msg_iovlen == 0)
+ {
+ return -EINVAL;
+ }
+
+ buf = msg->msg_iov->iov_base;
+ len = msg->msg_iov->iov_len;
+
if (msg->msg_iovlen == 1)
{
return to ? inet_sendto(psock, buf, len, flags, to, tolen) :
inet_send(psock, buf, len, flags);
}
+ /* If this is a connected stream socket (TCP), we can send each iov chunk
+ * sequentially without allocating a temporary memory buffer.
+ */
+
+ if (psock->s_type == SOCK_STREAM && to == NULL)
+ {
+ ssize_t total = 0;
+
+ end = &msg->msg_iov[msg->msg_iovlen];
+ for (iov = msg->msg_iov; iov != end; iov++)
+ {
+ if (iov->iov_len == 0 || iov->iov_base == NULL)
+ {
+ continue;
+ }
+
+ ret = inet_send(psock, iov->iov_base, iov->iov_len, flags);
Review Comment:
With CONFIG_NET_TCP_WRITE_BUFFERS=y each iov is still a separate
inet_send(), and psock_tcp_send() takes the connection lock for each call. A
send() from another thread can thus still put its data between the iovs of one
sendmsg(); before this PR the whole message went into one psock_tcp_send().
Fix: keep the gather path for TCP also with write buffers, or queue all iovs
under one lock.
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