net: sockets: Update msg_controllen in recvmsg properly

According to recvmsg man page, msg_controllen should be set to the sum
of the length of all control messages in the buffer.
This is missing from the current recvmsg implementation.
This commit aims to fix this by updating msg_controllen each time control
data are added to the buffer.
This commit also fixes cases where the msg_controllen is not cleared
correctly.

Fixes #77303

Signed-off-by: Axel Le Bourhis <axel.lebourhis@nxp.com>

subsys/net/lib/sockets/sockets.c

@@ -1322,12 +1322,14 @@ static int insert_pktinfo(struct msghdr *msg, int level, int type,
 			  void *pktinfo, size_t pktinfo_len)
 {
 	struct cmsghdr *cmsg;
+	size_t cmsg_space = 0;
 
 	if (msg->msg_controllen < pktinfo_len) {
 		return -EINVAL;
 	}
 
 	for (cmsg = CMSG_FIRSTHDR(msg); cmsg != NULL; cmsg = CMSG_NXTHDR(msg, cmsg)) {
+		cmsg_space += cmsg->cmsg_len;
 		if (cmsg->cmsg_len == 0) {
 			break;
 		}
@@ -1343,6 +1345,11 @@ static int insert_pktinfo(struct msghdr *msg, int level, int type,
 
 	memcpy(CMSG_DATA(cmsg), pktinfo, pktinfo_len);
 
+	/* msg_controllen should be set to the sum of the length of all control messages in the buffer
+	 * so updating this field each time control data is inserted */
+	cmsg_space += cmsg->cmsg_len;
+	msg->msg_controllen = cmsg_space;
+
 	return 0;
 }
 
@@ -1572,24 +1579,30 @@ static inline ssize_t zsock_recv_dgram(struct net_context *ctx,
 	if (msg != NULL) {
 		if (msg->msg_control != NULL) {
 			if (msg->msg_controllen > 0) {
-				bool clear_controllen = true;
+				bool clear_controllen = false;
 
 				if (IS_ENABLED(CONFIG_NET_CONTEXT_TIMESTAMPING)) {
-					clear_controllen = false;
 					if (add_timestamping(ctx, pkt, msg) < 0) {
 						msg->msg_flags |= ZSOCK_MSG_CTRUNC;
+					} else {
+						clear_controllen = false;
 					}
+				} else {
+					clear_controllen = true;
 				}
 
 				if (IS_ENABLED(CONFIG_NET_CONTEXT_RECV_PKTINFO) &&
 				    net_context_is_recv_pktinfo_set(ctx)) {
-					clear_controllen = false;
 					if (add_pktinfo(ctx, pkt, msg) < 0) {
 						msg->msg_flags |= ZSOCK_MSG_CTRUNC;
+					} else {
+						clear_controllen = false;
 					}
+				} else {
+					clear_controllen = true;
 				}
 
-				if (clear_controllen) {
+				if(clear_controllen) {
 					msg->msg_controllen = 0;
 				}
 			}