From: Nick Mathewson <nickm@torproject.org>
Date: Wed, 11 Feb 2009 17:24:11 +0000 (+0000)
Subject: New bind-to option to allow DNS clients to bind to arbitrary ports for their outgoing... 
X-Git-Tag: release-2.0.1-alpha~67
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=77c80b8dcf26b2cef66bce03cb25835a9a939306;p=libevent

New bind-to option to allow DNS clients to bind to arbitrary ports for their outgoing addresses.

svn:r1119
---

diff --git a/ChangeLog b/ChangeLog
index ecd3bcd0..3192bbff 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -142,6 +142,7 @@ Changes in current version:
  o Change the semantics of timeouts in conjunction with EV_PERSIST; timeouts in that case will now repeat until deleted.
  o sendfile, mmap and memory reference support for evbuffers.
  o New evutil_make_listen_socket_reuseable() to abstract SO_REUSEADDR.
+ o New bind-to option to allow DNS clients to bind to an arbitrary port for outgoing requests.
 
 Changes in 1.4.0:
  o allow \r or \n individually to separate HTTP headers instead of the standard "\r\n"; from Charles Kerr.
diff --git a/evdns.c b/evdns.c
index 166a0caf..c868fc01 100644
--- a/evdns.c
+++ b/evdns.c
@@ -318,6 +318,11 @@ struct evdns_base {
 	/* true iff we will use the 0x20 hack to prevent poisoning attacks. */
 	int global_randomize_case;
 
+	/** Port to bind to for outgoing DNS packets. */
+	struct sockaddr_storage global_outgoing_address;
+	/** Socklen_t for global_outgoing_address. 0 if it isn't set. */
+	socklen_t global_outgoing_addrlen;
+
 	struct search_state *global_search_state;
 };
 
@@ -2231,6 +2236,17 @@ _evdns_nameserver_add_impl(struct evdns_base *base, const struct sockaddr *addre
 	ns->socket = socket(PF_INET, SOCK_DGRAM, 0);
 	if (ns->socket < 0) { err = 1; goto out1; }
 	evutil_make_socket_nonblocking(ns->socket);
+
+	if (base->global_outgoing_addrlen) {
+		if (bind(ns->socket,
+			(struct sockaddr*)&base->global_outgoing_address,
+			base->global_outgoing_addrlen) < 0) {
+			log(EVDNS_LOG_WARN,"Couldn't bind to outgoing address");
+			err = 2;
+			goto out2;
+		}
+	}
+
 	if (connect(ns->socket, address, addrlen) != 0) {
 		err = 2;
 		goto out2;
@@ -2955,6 +2971,15 @@ evdns_base_set_option(struct evdns_base *base,
 		int randcase = strtoint(val);
 		if (!(flags & DNS_OPTION_MISC)) return 0;
 		base->global_randomize_case = randcase;
+	} else if (!strncmp(option, "bind-to:", 8)) {
+                /* XXX This only applies to successive nameservers, not
+                 * to already-configured ones.  We might want to fix that. */
+                int len = sizeof(base->global_outgoing_address);
+		if (!(flags & DNS_OPTION_NAMESERVERS)) return 0;
+		if (evutil_parse_sockaddr_port(val,
+			(struct sockaddr*)&base->global_outgoing_address, &len))
+                        return -1;
+                base->global_outgoing_addrlen = len;
 	}
 	return 0;
 }
diff --git a/include/event2/dns.h b/include/event2/dns.h
index b9b47e82..7920c3e9 100644
--- a/include/event2/dns.h
+++ b/include/event2/dns.h
@@ -395,7 +395,10 @@ void evdns_cancel_request(struct evdns_base *base, struct evdns_request *req);
 
   The currently available configuration options are:
 
-    ndots, timeout, max-timeouts, max-inflight, attempts, randomize-case.
+    ndots, timeout, max-timeouts, max-inflight, attempts, randomize-case,
+    bind-to.
+
+  The option name needs to end with a colon.
 
   @param base the evdns_base to which to apply this operation
   @param option the name of the configuration option to be modified