net: Cherry-pick TCP and mDNS regressions bugfixes

subsys/net/ip/tcp.c

@@ -2719,8 +2719,8 @@
 }
 
 static enum net_verdict tcp_data_received(struct tcp *conn, struct net_pkt *pkt,
-					  size_t *len, bool psh)
+					  size_t *len, bool psh, bool fin)
 {
 	enum net_verdict ret;
 
 	if (*len == 0) {
@@ -2732,6 +2732,13 @@
 	net_stats_update_tcp_seg_recv(conn->iface);
 	conn_ack(conn, *len);
 
+	/* In case FIN was received, don't send ACK just yet, FIN,ACK will be
+	 * sent instead.
+	 */
+	if (fin) {
+		return ret;
+	}
+
 	/* Delay ACK response in case of small window or missing PSH,
 	 * as described in RFC 813.
 	 */
@@ -3143,37 +3150,8 @@
 		}
 
 		break;
-	case TCP_ESTABLISHED:
-		/* full-close */
-		if (FL(&fl, &, FIN, th_seq(th) == conn->ack)) {
-			if (len) {
-				verdict = tcp_data_get(conn, pkt, &len);
-				if (verdict == NET_OK) {
-					/* net_pkt owned by the recv fifo now */
-					pkt = NULL;
-				}
-			} else {
-				verdict = NET_OK;
-			}
-
-			conn_ack(conn, + len + 1);
-			keep_alive_timer_stop(conn);
-
-			if (net_tcp_seq_cmp(th_ack(th), conn->seq) > 0) {
-				uint32_t len_acked = th_ack(th) - conn->seq;
-
-				conn_seq(conn, + len_acked);
-			}
-
-			tcp_out(conn, FIN | ACK);
-			conn_seq(conn, + 1);
-			tcp_setup_retransmission(conn);
-
-			tcp_setup_last_ack_timer(conn);
-			next = TCP_LAST_ACK;
-
-			break;
-		}
+	case TCP_ESTABLISHED: {
+		bool fin = FL(&fl, &, FIN, th_seq(th) == conn->ack);
 
 		/* Whatever we've received, we know that peer is alive, so reset
 		 * the keepalive timer.
@@ -3279,11 +3257,21 @@
 
 			/* We are closing the connection, send a FIN to peer */
 			if (conn->in_close && conn->send_data_total == 0) {
-				next = TCP_FIN_WAIT_1;
-
-				k_work_reschedule_for_queue(&tcp_work_q,
-							    &conn->fin_timer,
-							    FIN_TIMEOUT);
+				if (fin) {
+					/* If FIN was also present in the processed
+					 * packet, acknowledge that and jump directly
+					 * to TCP_LAST_ACK.
+					 */
+					conn_ack(conn, + 1);
+					next = TCP_LAST_ACK;
+					tcp_setup_last_ack_timer(conn);
+				} else {
+					/* Otherwise, wait for FIN in TCP_FIN_WAIT_1 */
+					next = TCP_FIN_WAIT_1;
+					k_work_reschedule_for_queue(&tcp_work_q,
+								    &conn->fin_timer,
+								    FIN_TIMEOUT);
+				}
 
 				tcp_out(conn, FIN | ACK);
 				conn_seq(conn, + 1);
@@ -3314,7 +3302,7 @@
 data_recv:
 				psh = FL(&fl, &, PSH);
 
-				verdict = tcp_data_received(conn, pkt, &len, psh);
+				verdict = tcp_data_received(conn, pkt, &len, psh, fin);
 				if (verdict == NET_OK) {
 					/* net_pkt owned by the recv fifo now */
 					pkt = NULL;
@@ -3358,7 +3346,19 @@
 			k_sem_give(&conn->tx_sem);
 		}
 
+		/* Finally, after all Data/ACK processing, check for FIN flag. */
+		if (fin) {
+			keep_alive_timer_stop(conn);
+			conn_ack(conn, + 1);
+			tcp_out(conn, FIN | ACK);
+			conn_seq(conn, + 1);
+			tcp_setup_retransmission(conn);
+			tcp_setup_last_ack_timer(conn);
+			next = TCP_LAST_ACK;
+		}
+
 		break;
+	}
 	case TCP_CLOSE_WAIT:
 		/* Half-close is not supported, so do nothing here */
 		break;

subsys/net/lib/dns/llmnr_responder.c

@@ -192,23 +192,19 @@
 
 static void add_question(struct net_buf *query, enum dns_rr_type qtype)
 {
-	char *dot = query->data + DNS_MSG_HEADER_SIZE;
-	char *prev = NULL;
+	char *dot = query->data + DNS_MSG_HEADER_SIZE + 1;
+	char *prev = query->data + DNS_MSG_HEADER_SIZE;
 	uint16_t offset;
 
-	while ((dot = strchr(dot, '.'))) {
-		if (!prev) {
-			prev = dot++;
-			continue;
-		}
+	/* For the length of the first label. */
+	query->len += 1;
 
+	while ((dot = strchr(dot, '.')) != NULL) {
 		*prev = dot - prev - 1;
 		prev = dot++;
 	}
 
-	if (prev) {
-		*prev = strlen(prev) - 1;
-	}
+	*prev = strlen(prev + 1);
 
 	offset = DNS_MSG_HEADER_SIZE + query->len + 1;
 	UNALIGNED_PUT(htons(qtype), (uint16_t *)(query->data+offset));
@@ -245,14 +241,15 @@
 	/* Prepare the response into the query buffer: move the name
 	 * query buffer has to get enough free space: dns_hdr + query + answer
 	 */
-	if ((net_buf_max_len(query) - query->len) < (DNS_MSG_HEADER_SIZE +
+	if ((net_buf_max_len(query) - query->len) < (DNS_MSG_HEADER_SIZE + 1 +
 					  (DNS_QTYPE_LEN + DNS_QCLASS_LEN) * 2 +
 					  DNS_TTL_LEN + DNS_RDLENGTH_LEN +
 					  addr_len + query->len)) {
 		return -ENOBUFS;
 	}
 
-	memmove(query->data + DNS_MSG_HEADER_SIZE, query->data, query->len);
+	/* +1 for the initial label length */
+	memmove(query->data + DNS_MSG_HEADER_SIZE + 1, query->data, query->len);
 
 	setup_dns_hdr(query->data, 1, dns_id);
 
@@ -488,8 +485,8 @@
 			result->data, ret);
 
 		/* If the query matches to our hostname, then send reply */
-		if (!strncasecmp(hostname, result->data + 1, hostname_len) &&
-		    (result->len - 1) >= hostname_len) {
+		if (!strncasecmp(hostname, result->data, hostname_len) &&
+		    (result->len) >= hostname_len) {
 			NET_DBG("%s query to our hostname %s", "LLMNR",
 				hostname);
 			ret = send_response(sock, src_addr, addrlen, result, qtype,

subsys/net/lib/dns/mdns_responder.c

@@ -274,23 +274,19 @@
 static void add_answer(struct net_buf *query, enum dns_rr_type qtype,
 		       uint32_t ttl, uint16_t addr_len, uint8_t *addr)
 {
-	char *dot = query->data + DNS_MSG_HEADER_SIZE;
-	char *prev = NULL;
+	char *dot = query->data + DNS_MSG_HEADER_SIZE + 1;
+	char *prev = query->data + DNS_MSG_HEADER_SIZE;
 	uint16_t offset;
 
-	while ((dot = strchr(dot, '.'))) {
-		if (!prev) {
-			prev = dot++;
-			continue;
-		}
+	/* For the length of the first label. */
+	query->len += 1;
 
+	while ((dot = strchr(dot, '.')) != NULL) {
 		*prev = dot - prev - 1;
 		prev = dot++;
 	}
 
-	if (prev) {
-		*prev = strlen(prev) - 1;
-	}
+	*prev = strlen(prev + 1);
 
 	/* terminator byte (0x00) */
 	query->len += 1;
@@ -322,14 +318,15 @@
 	/* Prepare the response into the query buffer: move the name
 	 * query buffer has to get enough free space: dns_hdr + answer
 	 */
-	if ((net_buf_max_len(query) - query->len) < (DNS_MSG_HEADER_SIZE +
+	if ((net_buf_max_len(query) - query->len) < (DNS_MSG_HEADER_SIZE + 1 +
 					  DNS_QTYPE_LEN + DNS_QCLASS_LEN +
 					  DNS_TTL_LEN + DNS_RDLENGTH_LEN +
 					  addr_len)) {
 		return -ENOBUFS;
 	}
 
-	memmove(query->data + DNS_MSG_HEADER_SIZE, query->data, query->len);
+	/* +1 for the initial label length */
+	memmove(query->data + DNS_MSG_HEADER_SIZE + 1, query->data, query->len);
 
 	setup_dns_hdr(query->data, 1);
 
@@ -641,7 +638,7 @@
 		}
 
 		/* Handle only .local queries */
-		lquery = strrchr(result->data + 1, '.');
+		lquery = strrchr(result->data, '.');
 		if (!lquery || memcmp(lquery, (const void *){ ".local" }, 7)) {
 			continue;
 		}
@@ -654,9 +651,9 @@
 		 * We skip the first dot, and make sure there is dot after
 		 * matching hostname.
 		 */
-		if (!strncasecmp(hostname, result->data + 1, hostname_len) &&
-		    (result->len - 1) >= hostname_len &&
-		    &(result->data + 1)[hostname_len] == lquery) {
+		if (!strncasecmp(hostname, result->data, hostname_len) &&
+		    (result->len) >= hostname_len &&
+		    &result->data[hostname_len] == lquery) {
 			NET_DBG("%s %s %s to our hostname %s%s", "mDNS",
 				family == AF_INET ? "IPv4" : "IPv6", "query",
 				hostname, ".local");
@@ -664,7 +661,7 @@
 				      result, qtype);
 		} else if (IS_ENABLED(CONFIG_MDNS_RESPONDER_DNS_SD)
 			&& qtype == DNS_RR_TYPE_PTR) {
 			send_sd_response(sock, family, src_addr, addrlen,
 					 &dns_msg, result);
 		}
 

tests/net/socket/getaddrinfo/src/main.c

@@ -96,9 +96,9 @@
 	/* In this test we are just checking if the query came to us in correct
 	 * form, we are not creating a DNS server implementation here.
 	 */
-	if (strncmp(result->data + 1, QUERY_HOST,
+	if (strncmp(result->data, QUERY_HOST,
 		    sizeof(QUERY_HOST) - 1)) {
 		net_buf_unref(result);
 		return false;
 	}