Implement source address selection

This commit introduces a '-S' command line option and a "bind" configuration
file option for selecting the source address when making outbound TCP
connections (similar to the corresponding option in catgirl(1)).

4 files changed, 43 insertions, 9 deletions

diff --git a/bounce.c b/bounce.c
index eef6c12..19e2dd4 100644
--- a/bounce.c
+++ b/bounce.c
@@ -258,6 +258,7 @@ int main(int argc, char *argv[]) {
 	bool insecure = false;
 	const char *clientCert = NULL;
 	const char *clientPriv = NULL;
+	const char *serverBindHost = NULL;
 
 	const char *host = NULL;
 	const char *port = "6697";
@@ -271,7 +272,7 @@ int main(int argc, char *argv[]) {
 	const char *join = NULL;
 	const char *quit = "connection reset by purr";
 
-	const char *Opts = "!A:C:H:K:NP:U:W:a:c:ef:g:h:j:k:n:p:q:r:s:u:vw:xy:";
+	const char *Opts = "!A:C:H:K:NP:S:U:W:a:c:ef:g:h:j:k:n:p:q:r:s:u:vw:xy:";
 	const struct option LongOpts[] = {
 		{ "insecure", no_argument, NULL, '!' },
 		{ "local-ca", required_argument, NULL, 'A' },
@@ -280,6 +281,7 @@ int main(int argc, char *argv[]) {
 		{ "local-priv", required_argument, NULL, 'K' },
 		{ "no-names", no_argument, NULL, 'N' },
 		{ "local-port", required_argument, NULL, 'P' },
+		{ "bind", required_argument, NULL, 'S' },
 		{ "local-path", required_argument, NULL, 'U' },
 		{ "local-pass", required_argument, NULL, 'W' },
 		{ "sasl-plain", required_argument, NULL, 'a' },
@@ -321,6 +323,7 @@ int main(int argc, char *argv[]) {
 			break; case 'K': strlcpy(privPath, optarg, sizeof(privPath));
 			break; case 'N': stateNoNames = true;
 			break; case 'P': bindPort = optarg;
+			break; case 'S': serverBindHost = optarg;
 			break; case 'U': strlcpy(bindPath, optarg, sizeof(bindPath));
 			break; case 'W': clientPass = optarg;
 			break; case 'a': sasl = true; plain = optarg;
@@ -403,7 +406,7 @@ int main(int argc, char *argv[]) {
 		: localBind(bind, ARRAY_LEN(bind), bindHost, bindPort);
 
 	serverConfig(insecure, clientCert, clientPriv);
-	int server = serverConnect(host, port);
+	int server = serverConnect(serverBindHost, host, port);
 
 #ifdef __FreeBSD__
 	int error = cap_enter();
diff --git a/bounce.h b/bounce.h
index a0f9160..20d7d40 100644
--- a/bounce.h
+++ b/bounce.h
@@ -133,7 +133,7 @@ size_t localUnix(int fds[], size_t cap, const char *path);
 struct tls *localAccept(int *fd, int bind);
 
 void serverConfig(bool insecure, const char *cert, const char *priv);
-int serverConnect(const char *host, const char *port);
+int serverConnect(const char *bindHost, const char *host, const char *port);
 void serverRecv(void);
 void serverSend(const char *ptr, size_t len);
 void serverFormat(const char *format, ...)
diff --git a/pounce.1 b/pounce.1
index 275b5a6..c55310b 100644
--- a/pounce.1
+++ b/pounce.1
@@ -1,4 +1,4 @@
-.Dd January 17, 2020
+.Dd February 18, 2020
 .Dt POUNCE 1
 .Os
 .
@@ -14,6 +14,7 @@
 .Op Fl H Ar host
 .Op Fl K Ar priv
 .Op Fl P Ar port
+.Op Fl S Ar bind
 .Op Fl U Ar unix
 .Op Fl W Ar pass
 .Op Fl a Ar auth
@@ -121,6 +122,11 @@ Bind to
 .Ar port .
 The default port is 6697.
 .
+.It Fl S Ar host , Cm bind = Ar host
+Bind to source address
+.Ar host
+when connecting to the server.
+.
 .It Fl U Ar path , Cm local-path = Ar path
 Bind to a UNIX-domain socket at
 .Ar path .
diff --git a/server.c b/server.c
index ce5ae87..2bb897d 100644
--- a/server.c
+++ b/server.c
@@ -63,22 +63,47 @@ void serverConfig(bool insecure, const char *cert, const char *priv) {
 	tls_config_free(config);
 }
 
-int serverConnect(const char *host, const char *port) {
+int serverConnect(const char *bindHost, const char *host, const char *port) {
 	assert(client);
 
+	int error;
+	int sock = -1;
 	struct addrinfo *head;
 	struct addrinfo hints = {
 		.ai_family = AF_UNSPEC,
 		.ai_socktype = SOCK_STREAM,
 		.ai_protocol = IPPROTO_TCP,
 	};
-	int error = getaddrinfo(host, port, &hints, &head);
+
+	if (bindHost) {
+		error = getaddrinfo(bindHost, NULL, &hints, &head);
+		if (error) errx(EX_NOHOST, "%s: %s", bindHost, gai_strerror(error));
+
+		for (struct addrinfo *ai = head; ai; ai = ai->ai_next) {
+			sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
+			if (sock < 0) err(EX_OSERR, "socket");
+
+			error = bind(sock, ai->ai_addr, ai->ai_addrlen);
+			if (!error) {
+				hints.ai_family = ai->ai_family;
+				break;
+			}
+
+			close(sock);
+			sock = -1;
+		}
+		if (sock < 0) err(EX_UNAVAILABLE, "%s", bindHost);
+		freeaddrinfo(head);
+	}
+
+	error = getaddrinfo(host, port, &hints, &head);
 	if (error) errx(EX_NOHOST, "%s:%s: %s", host, port, gai_strerror(error));
 
-	int sock = -1;
 	for (struct addrinfo *ai = head; ai; ai = ai->ai_next) {
-		sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
-		if (sock < 0) err(EX_OSERR, "socket");
+		if (sock < 0) {
+			sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
+			if (sock < 0) err(EX_OSERR, "socket");
+		}
 
 		error = connect(sock, ai->ai_addr, ai->ai_addrlen);
 		if (!error) break;