Clarify the send_mtu_probe() function.

[tinc] / src / net_packet.c

diff --git a/src/net_packet.c b/src/net_packet.c
index c07dd1a..5626e84 100644 (file)
--- a/src/net_packet.c
+++ b/src/net_packet.c
@@ -46,6 +46,10 @@
 #include "utils.h"
 #include "xalloc.h"
 
+#ifndef MAX
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+#endif
+
 int keylifetime = 0;
 #ifdef HAVE_LZO
 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
@@ -58,27 +62,21 @@ bool localdiscovery = true;
 
 #define MAX_SEQNO 1073741824
 
-/* mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
-   mtuprobes ==    31: sleep pinginterval seconds
-   mtuprobes ==    32: send 1 burst, sleep pingtimeout second
-   mtuprobes ==    33: no response from other side, restart PMTU discovery process
-
-   Probes are sent in batches of at least three, with random sizes between the
-   lower and upper boundaries for the MTU thus far discovered.
-
-   After the initial discovery, a fourth packet is added to each batch with a
-   size larger than the currently known PMTU, to test if the PMTU has increased.
+static void send_mtu_probe_packet(node_t *n, int len) {
+       vpn_packet_t packet;
+       packet.offset = DEFAULT_PACKET_OFFSET;
+       memset(DATA(&packet), 0, 14);
+       randomize(DATA(&packet) + 14, len - 14);
+       packet.len = len;
+       packet.priority = 0;
 
-   In case local discovery is enabled, another packet is added to each batch,
-   which will be broadcast to the local network.
+       logger(DEBUG_TRAFFIC, LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
 
-*/
+       send_udppacket(n, &packet);
+}
 
 static void send_mtu_probe_handler(void *data) {
        node_t *n = data;
-       int timeout = 1;
-
-       n->mtuprobes++;
 
        if(!n->status.reachable || !n->status.validkey) {
                logger(DEBUG_TRAFFIC, LOG_INFO, "Trying to send MTU probe to unreachable or rekeying node %s (%s)", n->name, n->hostname);
@@ -86,6 +84,14 @@ static void send_mtu_probe_handler(void *data) {
                return;
        }
 
+       /* mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
+          mtuprobes ==    31: sleep pinginterval seconds
+          mtuprobes ==    32: send 1 burst, sleep pingtimeout second
+          mtuprobes ==    33: no response from other side, restart PMTU discovery process */
+
+       n->mtuprobes++;
+       int timeout = 1;
+
        if(n->mtuprobes > 32) {
                if(!n->minmtu) {
                        n->mtuprobes = 31;
@@ -122,36 +128,29 @@ static void send_mtu_probe_handler(void *data) {
                timeout = pingtimeout;
        }
 
-       for(int i = 0; i < 4 + localdiscovery; i++) {
-               int len;
+       /* After the initial discovery, a fourth packet is added to each batch with a
+          size larger than the currently known PMTU, to test if the PMTU has increased. */
+       if (n->mtuprobes >= 30 && n->maxmtu + 8 < MTU)
+               send_mtu_probe_packet(n, n->maxmtu + 8);
 
-               if(i == 0) {
-                       if(n->mtuprobes < 30 || n->maxmtu + 8 >= MTU)
-                               continue;
-                       len = n->maxmtu + 8;
-               } else if(n->maxmtu <= n->minmtu) {
-                       len = n->maxmtu;
-               } else {
+       /* Probes are sent in batches of three, with random sizes between the
+          lower and upper boundaries for the MTU thus far discovered. */
+       for (int i = 0; i < 3; i++) {
+               int len = n->maxmtu;
+               if(n->minmtu < n->maxmtu)
                        len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
-               }
-
-               if(len < 64)
-                       len = 64;
 
-               vpn_packet_t packet;
-               packet.offset = DEFAULT_PACKET_OFFSET;
-               memset(DATA(&packet), 0, 14);
-               randomize(DATA(&packet) + 14, len - 14);
-               packet.len = len;
-               packet.priority = 0;
-               n->status.send_locally = i >= 4 && n->mtuprobes <= 10 && n->prevedge;
-
-               logger(DEBUG_TRAFFIC, LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
+               send_mtu_probe_packet(n, MAX(len, 64));
+       }
 
-               send_udppacket(n, &packet);
+       /* In case local discovery is enabled, another packet is added to each batch,
+          which will be broadcast to the local network. */
+       if(localdiscovery && n->mtuprobes <= 10 && n->prevedge) {
+               n->status.send_locally = true;
+               send_mtu_probe_packet(n, 16);
+               n->status.send_locally = false;
        }
 
-       n->status.send_locally = false;
        n->probe_counter = 0;
        gettimeofday(&n->probe_time, NULL);