Add an option to set source address for a BGP session.

When adding a BGP neighbour, one can set "update-source" (quagga syntax) to the
source IP address that will be used for that session.

Signed-off-by: Benjamin Cama <benoar@dolka.fr>

bgp.c

@@ -95,7 +95,7 @@ int bgp_setup(int as)
 
 /* start connection with a peer */
 int bgp_start(struct bgp_peer *peer, char *name, int as, int keepalive,
-    int hold, int enable)
+    int hold, struct in_addr update_source, int enable)
 {
     struct hostent *h;
     int ibgp;
@@ -124,6 +124,7 @@ int bgp_start(struct bgp_peer *peer, char *name, int as, int keepalive,
     }
 
     memcpy(&peer->addr, h->h_addr, sizeof(peer->addr));
+    peer->source_addr = update_source.s_addr;
     peer->as = as > 0 ? as : our_as;
     ibgp = peer->as == our_as;
 
@@ -696,6 +697,7 @@ static int bgp_connect(struct bgp_peer *peer)
 {
     static int bgp_port = 0;
     struct sockaddr_in addr;
+    struct sockaddr_in source_addr;
     struct epoll_event ev;
 
     if (!bgp_port)
@@ -727,6 +729,19 @@ static int bgp_connect(struct bgp_peer *peer)
     /* set to non-blocking */
     fcntl(peer->sock, F_SETFL, fcntl(peer->sock, F_GETFL, 0) | O_NONBLOCK);
 
+    /* set source address */
+    memset(&source_addr, 0, sizeof(source_addr));
+    source_addr.sin_family = AF_INET;
+    source_addr.sin_addr.s_addr = peer->source_addr; /* defaults to INADDR_ANY */
+    if (bind(peer->sock, (struct sockaddr *) &source_addr, sizeof(source_addr)) < 0)
+    {
+	LOG(1, 0, 0, "Can't set source address to %s: %s\n",
+	    inet_ntoa(source_addr.sin_addr), strerror(errno));
+
+	bgp_set_retry(peer);
+	return 0;
+    }
+
     /* try connect */
     memset(&addr, 0, sizeof(addr));
     addr.sin_family = AF_INET;

bgp.h

@@ -152,6 +152,7 @@ struct bgp_buf {
 struct bgp_peer {
     char name[32];			/* peer name */
     in_addr_t addr;			/* peer address */
+    in_addr_t source_addr;		/* our source address */
     int as;				/* AS number */
     int sock;
     enum bgp_state state;		/* FSM state */
@@ -188,7 +189,7 @@ extern int bgp_configured;
 /* actions */
 int bgp_setup(int as);
 int bgp_start(struct bgp_peer *peer, char *name, int as, int keepalive,
-    int hold, int enable);
+    int hold, struct in_addr update_source, int enable);
 
 void bgp_stop(struct bgp_peer *peer);
 void bgp_halt(struct bgp_peer *peer);

cli.c

@@ -1038,6 +1038,11 @@ static int cmd_show_run(struct cli_def *cli, char *command, char **argv, int arg
 				h = BGP_HOLD_TIME;
 
 			cli_print(cli, " neighbour %s timers %d %d", config->neighbour[i].name, k, h);
+
+			if (config->neighbour[i].update_source.s_addr != INADDR_ANY)
+				cli_print(cli, " neighbour %s update-source %s",
+						config->neighbour[i].name,
+						inet_ntoa(config->neighbour[i].update_source));
 		}
 	}
 #endif
@@ -2064,6 +2069,7 @@ static int cmd_router_bgp_neighbour(struct cli_def *cli, char *command, char **a
 			return cli_arg_help(cli, 0,
 				"remote-as", "Set remote autonomous system number",
 				"timers",    "Set timers",
+				"update-source",    "Set source address to use for the BGP session",
 				NULL);
 
 		default:
@@ -2082,6 +2088,9 @@ static int cmd_router_bgp_neighbour(struct cli_def *cli, char *command, char **a
 					return cli_arg_help(cli, 1, NULL);
 			}
 
+			if (MATCH("update-source", argv[1]))
+				return cli_arg_help(cli, argc > 3, "A.B.C.D", "Source IP address", NULL);
+
 			return CLI_OK;
 		}
 	}
@@ -2118,12 +2127,33 @@ static int cmd_router_bgp_neighbour(struct cli_def *cli, char *command, char **a
 			snprintf(config->neighbour[i].name, sizeof(config->neighbour[i].name), "%s", argv[0]);
 			config->neighbour[i].keepalive = -1;
 			config->neighbour[i].hold = -1;
+			config->neighbour[i].update_source.s_addr = INADDR_ANY;
 		}
 
 		config->neighbour[i].as = as;
 		return CLI_OK;
 	}
 
+	if (MATCH("update-source", argv[1]))
+	{
+		struct in_addr addr;
+
+		if (!config->neighbour[i].name[0])
+		{
+			cli_error(cli, "Specify remote-as first");
+			return CLI_OK;
+		}
+
+		if (!inet_aton(argv[2], &addr))
+		{
+			cli_error(cli, "Cannot parse IP \"%s\"", argv[2]);
+			return CLI_OK;
+		}
+
+		config->neighbour[i].update_source = addr;
+		return CLI_OK;
+	}
+
 	if (argc != 4 || !MATCH("timers", argv[1]))
 	{
 		cli_error(cli, "Invalid arguments");

l2tpns.c

@@ -3564,7 +3564,8 @@ static void mainloop(void)
 		if (config->neighbour[i].name[0])
 			bgp_start(&bgp_peers[i], config->neighbour[i].name,
 				config->neighbour[i].as, config->neighbour[i].keepalive,
-				config->neighbour[i].hold, 0); /* 0 = routing disabled */
+				config->neighbour[i].hold, config->neighbour[i].update_source,
+				0); /* 0 = routing disabled */
 	}
 #endif /* BGP */
 

l2tpns.h

@@ -723,6 +723,7 @@ typedef struct
 	    	uint16_t as;
 		int keepalive;
 		int hold;
+		struct in_addr update_source;
 	} neighbour[BGP_NUM_PEERS];
 #endif
 } configt;