From 46fa12e666badb79e480c4b2399787551f8266d0 Mon Sep 17 00:00:00 2001
From: Guus Sliepen <guus@tinc-vpn.org>
Date: Mon, 8 Dec 2014 00:58:09 +0100
Subject: [PATCH] Make UDP packet handling more efficient.

Limit the amount of address/ID lookups to the minimum in all cases:

1) Legacy packets, need an address lookup.
2) Indirect SPTPS packets, need an address lookup + two ID lookups.
3) Direct SPTPS packets, need an ID or an address lookup.

So we start with an address lookup. If the source is an 1.1 node, we know it's an SPTPS packet,
and then the check for direct packets is a simple check if dstid is zero. If not, do the srcid and dstid
lookup. If the source is an 1.0 node, we don't have to do anything else.

If the address is unknown, we first check whether it's from a 1.1 node by assuming it has a valid srcid
and verifying the packet. If not, use the old try_harder().
---
 src/net_packet.c | 90 ++++++++++++++++++++++++------------------------
 1 file changed, 45 insertions(+), 45 deletions(-)

diff --git a/src/net_packet.c b/src/net_packet.c
index 1691f31f..f1320925 100644
--- a/src/net_packet.c
+++ b/src/net_packet.c
@@ -1030,13 +1030,13 @@ void handle_incoming_vpn_data(void *data, int flags) {
 	vpn_packet_t pkt;
 	sptps_packet_t *spkt = (sptps_packet_t *)&pkt;
 	char *hostname;
-	sockaddr_t from = {{0}};
-	socklen_t fromlen = sizeof from;
-	node_t *n = NULL;
-	node_t *to = myself;
-	int len;
+	node_id_t nullid = {};
+	sockaddr_t addr = {};
+	socklen_t addrlen = sizeof addr;
+	node_t *from, *to;
+	bool direct = false;
 
-	len = recvfrom(ls->udp.fd, &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
+	int len = recvfrom(ls->udp.fd, &pkt.dstid, MAXSIZE, 0, &addr.sa, &addrlen);
 
 	if(len <= 0 || len > MAXSIZE) {
 		if(!sockwouldblock(sockerrno))
@@ -1046,64 +1046,64 @@ void handle_incoming_vpn_data(void *data, int flags) {
 
 	pkt.len = len;
 
-	sockaddrunmap(&from); /* Some braindead IPv6 implementations do stupid things. */
+	sockaddrunmap(&addr); /* Some braindead IPv6 implementations do stupid things. */
 
-	bool direct = false;
-	if(len >= sizeof spkt->dstid + sizeof spkt->srcid) {
-		n = lookup_node_id(&spkt->srcid);
-		if(n) {
-			node_id_t nullid = {};
-			if(memcmp(&spkt->dstid, &nullid, sizeof nullid) == 0) {
-				/* A zero dstid is used to indicate a direct, non-relayed packet. */
-				direct = true;
-			} else {
-				to = lookup_node_id(&spkt->dstid);
-				if(!to) {
-					logger(DEBUG_PROTOCOL, LOG_WARNING, "Received UDP packet presumably sent by %s (%s) but with unknown destination ID", n->name, n->hostname);
-					return;
-				}
-			}
-			pkt.len -= sizeof spkt->dstid + sizeof spkt->srcid;
-		}
-	}
-
-	if(to != myself) {
-		/* We are being asked to relay this packet. */
+	// Try to figure out who sent this packet.
 
-		/* Don't allow random strangers to relay through us. Note that we check for *any* known address since we are not necessarily the first relay. */
-		if (!lookup_node_udp(&from)) {
-			logger(DEBUG_PROTOCOL, LOG_WARNING, "Refusing to relay packet from (presumably) %s (%s) to (presumably) %s (%s) because the packet comes from an unknown address", n->name, n->hostname, to->name, to->hostname);
-			return;
-		}
-
-		send_sptps_data_priv(to, n, 0, spkt->data, pkt.len);
-		return;
-	}
+	node_t *n = lookup_node_udp(&addr);
 
 	if(!n) {
-		/* Most likely an old-style packet without node IDs. */
-		direct = true;
-		n = lookup_node_udp(&from);
+		// It might be from a 1.1 node, which might have a source ID in the packet.
+		from = lookup_node_id(&pkt.srcid);
+		if(from && !memcmp(&pkt.dstid, &nullid, sizeof nullid) && from->status.sptps) {
+			if(sptps_verify_datagram(&n->sptps, pkt.data, pkt.len))
+				n = from;
+			else
+				goto skip_harder;
+		}
 	}
 
 	if(!n)
-		n = try_harder(&from, &pkt);
+		n = try_harder(&addr, &pkt);
 
+skip_harder:
 	if(!n) {
 		if(debug_level >= DEBUG_PROTOCOL) {
-			hostname = sockaddr2hostname(&from);
+			hostname = sockaddr2hostname(&addr);
 			logger(DEBUG_PROTOCOL, LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
 			free(hostname);
 		}
 		return;
 	}
 
-	if(!receive_udppacket(n, &pkt))
+	if(n->status.sptps) {
+		if(memcmp(&pkt.dstid, &nullid, sizeof nullid)) {
+			direct = true;
+			from = n;
+			to = myself;
+		} else {
+			from = lookup_node_id(&pkt.srcid);
+			to = lookup_node_id(&pkt.dstid);
+		}
+		if(!from || !to) {
+			logger(DEBUG_PROTOCOL, LOG_WARNING, "Received UDP packet from %s (%s) with unknown source and/or destination ID", n->name, n->hostname);
+			return;
+		}
+		if(to != myself) {
+			send_sptps_data_priv(to, n, 0, pkt.data, pkt.len);
+			return;
+		}
+	} else {
+		direct = true;
+		from = n;
+	}
+
+	if(!receive_udppacket(from, &pkt))
 		return;
 
 	n->sock = ls - listen_socket;
-	if(direct && sockaddrcmp(&from, &n->address))
-		update_node_udp(n, &from);
+	if(direct && sockaddrcmp(&addr, &n->address))
+		update_node_udp(n, &addr);
 }
 
 void handle_device_data(void *data, int flags) {
-- 
2.20.1