Add the ability to dump all traffic going through route() over a control connection.

One can get the packet stream in pcap format, which can be decoded using
tcpdump, for example:

tincctl -n <netname> pcap | tcpdump -r -

src/connection.h

@@ -43,7 +43,8 @@ typedef struct connection_status_t {
 		int decryptin:1;			/* 1 if we have to decrypt incoming traffic */
 		int mst:1;				/* 1 if this connection is part of a minimum spanning tree */
 		int control:1;
-		int unused:22;
+		int pcap:1;
+		int unused:21;
 } connection_status_t;
 
 #include "edge.h"

src/control.c

@@ -24,7 +24,11 @@
 #include "control_common.h"
 #include "graph.h"
 #include "logger.h"
+#include "meta.h"
+#include "net.h"
 #include "protocol.h"
+#include "route.h"
+#include "splay_tree.h"
 #include "utils.h"
 #include "xalloc.h"
 
@@ -116,6 +120,11 @@ bool control_h(connection_t *c, char *request) {
 		case REQ_DUMP_TRAFFIC:
 			return dump_traffic(c);
 
+		case REQ_PCAP:
+			c->status.pcap = true;
+			pcap = true;
+			return true;
+
 		default:
 			return send_request(c, "%d %d", CONTROL, REQ_INVALID);
 	}

src/control_common.h

@@ -38,6 +38,7 @@ enum request_type {
 	REQ_CONNECT,
 	REQ_DISCONNECT,
 	REQ_DUMP_TRAFFIC,
+	REQ_PCAP,
 };
 
 #define TINC_CTL_VERSION_CURRENT 0

src/route.c

@@ -22,10 +22,12 @@
 
 #include "splay_tree.h"
 #include "connection.h"
+#include "control_common.h"
 #include "ethernet.h"
 #include "ipv4.h"
 #include "ipv6.h"
 #include "logger.h"
+#include "meta.h"
 #include "net.h"
 #include "protocol.h"
 #include "route.h"
@@ -39,6 +41,7 @@ bool priorityinheritance = false;
 int macexpire = 600;
 bool overwrite_mac = false;
 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
+bool pcap = false;
 
 /* Sizes of various headers */
 
@@ -860,7 +863,23 @@ static void route_mac(node_t *source, vpn_packet_t *packet) {
 	send_packet(subnet->owner, packet);
 }
 
+static void send_pcap(vpn_packet_t *packet) {
+	pcap = false;
+	for(splay_node_t *node = connection_tree->head; node; node = node->next) {
+		connection_t *c = node->data;
+		if(!c->status.pcap)
+			continue;
+		else
+			pcap = true;
+		if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, packet->len))
+			send_meta(c, (char *)packet->data, packet->len);
+	}
+}
+
 void route(node_t *source, vpn_packet_t *packet) {
+	if(pcap)
+		send_pcap(packet);
+
 	if(forwarding_mode == FMODE_KERNEL && source != myself) {
 		send_packet(myself, packet);
 		return;

src/route.h

@@ -42,6 +42,7 @@ extern bool directonly;
 extern bool overwrite_mac;
 extern bool priorityinheritance;
 extern int macexpire;
+extern bool pcap;
 
 extern mac_t mymac;
 

src/tincctl.c

@@ -98,6 +98,7 @@ static void usage(bool status) {
 #ifdef HAVE_CURSES
 				"  top                        Show real-time statistics\n"
 #endif
+				"  pcap                       Dump traffic in pcap format\n"
 				"\n");
 		printf("Report bugs to tinc@tinc-vpn.org.\n");
 	}
@@ -301,9 +302,10 @@ static void make_names(void) {
 	}
 }
 
+static char buffer[4096];
+static size_t blen = 0;
+
 bool recvline(int fd, char *line, size_t len) {
-	static char buffer[4096];
-	static size_t blen = 0;
 	char *newline = NULL;
 
 	while(!(newline = memchr(buffer, '\n', blen))) {
@@ -328,6 +330,23 @@ bool recvline(int fd, char *line, size_t len) {
 	return true;
 }
 
+bool recvdata(int fd, char *data, size_t len) {
+	while(blen < len) {
+		int result = recv(fd, buffer + blen, sizeof buffer - blen, 0);
+		if(result == -1 && errno == EINTR)
+			continue;
+		else if(result <= 0)
+			return false;
+		blen += result;
+	}
+
+	memcpy(data, buffer, len);
+	memmove(buffer, buffer + len, blen - len);
+	blen -= len;
+
+	return true;
+}
+
 bool sendline(int fd, char *format, ...) {
 	static char buffer[4096];
 	char *p = buffer;
@@ -357,6 +376,57 @@ bool sendline(int fd, char *format, ...) {
 	return true;	
 }
 
+void pcap(int fd, FILE *out) {
+	sendline(fd, "%d %d", CONTROL, REQ_PCAP);
+	char data[9018];
+
+	struct {
+		uint32_t magic;
+		uint16_t major;
+		uint16_t minor;
+		uint32_t tz_offset;
+		uint32_t tz_accuracy;
+		uint32_t snaplen;
+		uint32_t ll_type;
+	} header = {
+		0xa1b2c3d4,
+		2, 4,
+		0, 0,
+		sizeof data,
+		1,
+	};
+
+	struct {
+		uint32_t tv_sec;
+		uint32_t tv_usec;
+		uint32_t len;
+		uint32_t origlen;
+	} packet;
+
+	struct timeval tv;
+
+	fwrite(&header, sizeof header, 1, out);
+	fflush(out);
+
+	char line[32];
+	while(recvline(fd, line, sizeof line)) {
+		int code, req, len;
+		int n = sscanf(line, "%d %d %d", &code, &req, &len);
+		gettimeofday(&tv, NULL);
+		if(n != 3 || code != CONTROL || req != REQ_PCAP || len < 0 || len > sizeof data)
+			break;
+		if(!recvdata(fd, data, len))
+			break;
+		packet.tv_sec = tv.tv_sec;
+		packet.tv_usec = tv.tv_usec;
+		packet.len = len;
+		packet.origlen = len;
+		fwrite(&packet, sizeof packet, 1, out);
+		fwrite(data, len, 1, out);
+		fflush(out);
+	}
+}
+
 int main(int argc, char *argv[], char *envp[]) {
 	int fd;
 	int result;
@@ -636,6 +706,11 @@ int main(int argc, char *argv[], char *envp[]) {
 	}
 #endif
 
+	if(!strcasecmp(argv[optind], "pcap")) {
+		pcap(fd, stdout);
+		return 0;
+	}
+
 	fprintf(stderr, "Unknown command `%s'.\n", argv[optind]);
 	usage(true);