Re-link peers by IP when dnsmgr changes the IP

Asterisk's dnsmgr currently takes a pointer to an ast_sockaddr and updates it
anytime an address resolves to something different. There are a couple of
issues with this. First, the ast_sockaddr is usually the address of an
ast_sockaddr inside a refcounted struct and we never bump the refcount of those
structs when using dnsmgr. This makes it possible that a refresh could happen
after the destructor for that object is called (despite ast_dnsmgr_release
being called in that destructor). Second, the module using dnsmgr cannot be
aware of an address changing without polling for it in the code. If an action
needs to be taken on address update (like re-linking a SIP peer in the
peers_by_ip table), then polling for this change negates many of the benefits
of having dnsmgr in the first place.

This patch adds a function to the dnsmgr API that calls an update callback
instead of blindly updating the address itself. It also moves calls to
ast_dnsmgr_release outside of the destructor functions and into cleanup
functions that are called when we no longer need the objects and increments the
refcount of the objects using dnsmgr since those objects are stored on the
ast_dnsmgr_entry struct. A helper function for returning the proper default SIP
port (non-tls vs tls) is also added and used.

This patch also incorporates changes from a patch posted by Timo Teräs to
ASTERISK-19106 for related dnsmgr issues.

(closes issue ASTERISK-19106)

Review: https://reviewboard.asterisk.org/r/1691/
........

Merged revisions 353371 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 353397 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@353418 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 25 insertions, 6 deletions

diff --git a/main/dnsmgr.c b/main/dnsmgr.c
index d11cd99e3..7cdcd0ced 100644
--- a/main/dnsmgr.c
+++ b/main/dnsmgr.c
@@ -58,6 +58,10 @@ struct ast_dnsmgr_entry {
 	unsigned int family;
 	/*! Set to 1 if the entry changes */
 	unsigned int changed:1;
+	/*! Data to pass back to update_func */
+	void *data;
+	/*! The callback function to execute on address update */
+	dns_update_func update_func;
 	ast_mutex_t lock;
 	AST_RWLIST_ENTRY(ast_dnsmgr_entry) list;
 	/*! just 1 here, but we use calloc to allocate the correct size */
@@ -130,7 +134,7 @@ void ast_dnsmgr_release(struct ast_dnsmgr_entry *entry)
 	ast_free(entry);
 }
 
-int ast_dnsmgr_lookup(const char *name, struct ast_sockaddr *result, struct ast_dnsmgr_entry **dnsmgr, const char *service)
+static int internal_dnsmgr_lookup(const char *name, struct ast_sockaddr *result, struct ast_dnsmgr_entry **dnsmgr, const char *service, dns_update_func func, void *data)
 {
 	unsigned int family;
 
@@ -165,9 +169,21 @@ int ast_dnsmgr_lookup(const char *name, struct ast_sockaddr *result, struct ast_
 
 	ast_verb(3, "adding dns manager for '%s'\n", name);
 	*dnsmgr = ast_dnsmgr_get_family(name, result, service, family);
+	(*dnsmgr)->update_func = func;
+	(*dnsmgr)->data = data;
 	return !*dnsmgr;
 }
 
+int ast_dnsmgr_lookup(const char *name, struct ast_sockaddr *result, struct ast_dnsmgr_entry **dnsmgr, const char *service)
+{
+	return internal_dnsmgr_lookup(name, result, dnsmgr, service, NULL, NULL);
+}
+
+int ast_dnsmgr_lookup_cb(const char *name, struct ast_sockaddr *result, struct ast_dnsmgr_entry **dnsmgr, const char *service, dns_update_func func, void *data)
+{
+	return internal_dnsmgr_lookup(name, result, dnsmgr, service, func, data);
+}
+
 /*
  * Refresh a dnsmgr entry
  */
@@ -187,16 +203,19 @@ static int dnsmgr_refresh(struct ast_dnsmgr_entry *entry, int verbose)
 		if (!ast_sockaddr_port(&tmp)) {
 			ast_sockaddr_set_port(&tmp, ast_sockaddr_port(entry->result));
 		}
-
 		if (ast_sockaddr_cmp(&tmp, entry->result)) {
 			const char *old_addr = ast_strdupa(ast_sockaddr_stringify(entry->result));
 			const char *new_addr = ast_strdupa(ast_sockaddr_stringify(&tmp));
 
-			ast_log(LOG_NOTICE, "dnssrv: host '%s' changed from %s to %s\n",
-					entry->name, old_addr, new_addr);
+			if (entry->update_func) {
+				entry->update_func(entry->result, &tmp, entry->data);
+			} else {
+				ast_log(LOG_NOTICE, "dnssrv: host '%s' changed from %s to %s\n",
+						entry->name, old_addr, new_addr);
 
-			ast_sockaddr_copy(entry->result, &tmp);
-			changed = entry->changed = 1;
+				ast_sockaddr_copy(entry->result, &tmp);
+				changed = entry->changed = 1;
+			}
 		}
 	}