From 1a2e0d75eac159b2ed6d665e57044e842216eb2c Mon Sep 17 00:00:00 2001
From: Richard Fuchs <rfuchs@sipwise.com>
Date: Fri, 22 Feb 2013 14:45:59 -0500
Subject: [PATCH] create a random but constant "foundation" string for ice
 candidates

---
 daemon/main.c |  2 ++
 daemon/sdp.c  | 30 ++++++++++++++++++++++--------
 daemon/sdp.h  |  2 ++
 3 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/daemon/main.c b/daemon/main.c
index 1e60ba78e..fc058abcb 100644
--- a/daemon/main.c
+++ b/daemon/main.c
@@ -18,6 +18,7 @@
 #include "call.h"
 #include "kernel.h"
 #include "redis.h"
+#include "sdp.h"
 
 
 
@@ -330,6 +331,7 @@ static void init_everything() {
 	openlog("mediaproxy-ng", LOG_PID | LOG_NDELAY, LOG_DAEMON);
 	signals();
 	resources();
+	sdp_init();
 }
 
 void redis_mod_verify(void *dlh) {
diff --git a/daemon/sdp.c b/daemon/sdp.c
index 6b8acaca8..0b15ecd08 100644
--- a/daemon/sdp.c
+++ b/daemon/sdp.c
@@ -69,6 +69,9 @@ struct sdp_attribute {
 
 
 static const char ice_chars[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+static char ice_foundation[17];
+static str ice_foundation_str;
+
 
 
 
@@ -656,19 +659,20 @@ strip:
 	return 0;
 }
 
+static void random_string(char *buf, int len) {
+	while (len--)
+		*buf++ = ice_chars[random() % strlen(ice_chars)];
+}
+
 static void create_random_string(struct call *call, str *s, int len) {
 	char buf[30];
-	char *p;
 
 	assert(len < sizeof(buf));
 	if (s->s)
 		return;
 
-	p = buf;
-	while (len--)
-		*p++ = ice_chars[random() % strlen(ice_chars)];
-
-	call_str_cpy_len(call, s, buf, p - buf);
+	random_string(buf, len);
+	call_str_cpy_len(call, s, buf, len);
 }
 
 int sdp_replace(struct sdp_chopper *chop, GQueue *sessions, struct call *call,
@@ -748,10 +752,14 @@ int sdp_replace(struct sdp_chopper *chop, GQueue *sessions, struct call *call,
 			if (flags->ice_force) {
 				copy_up_to_end_of(chop, &media->s);
 				/* prio = (2^24) * 126 + (2^8) * 65535 + (256 - componentID) */
-				chopper_append_c(chop, "a=candidate:1 1 UDP 2130706431 ");
+				chopper_append_c(chop, "a=candidate:");
+				chopper_append_str(chop, &ice_foundation_str);
+				chopper_append_c(chop, " 1 UDP 2130706431 ");
 				insert_ice_address(chop, m, off, flags, 0);
 				chopper_append_c(chop, " typ host\r\n");
-				chopper_append_c(chop, "a=candidate:1 2 UDP 2130706430 ");
+				chopper_append_c(chop, "a=candidate:");
+				chopper_append_str(chop, &ice_foundation_str);
+				chopper_append_c(chop, " 2 UDP 2130706430 ");
 				insert_ice_address(chop, m, off, flags, 1);
 				chopper_append_c(chop, " typ host\r\n");
 			}
@@ -765,3 +773,9 @@ error:
 	mylog(LOG_ERROR, "Error rewriting SDP");
 	return -1;
 }
+
+void sdp_init() {
+	random_string(ice_foundation, sizeof(ice_foundation) - 1);
+	ice_foundation_str.s = ice_foundation;
+	ice_foundation_str.len = sizeof(ice_foundation) - 1;
+}
diff --git a/daemon/sdp.h b/daemon/sdp.h
index eb5dedcbf..25b8e4988 100644
--- a/daemon/sdp.h
+++ b/daemon/sdp.h
@@ -28,6 +28,8 @@ struct sdp_chopper {
 	int str_len;
 };
 
+void sdp_init(void);
+
 int sdp_parse(str *body, GQueue *sessions);
 int sdp_streams(const GQueue *sessions, GQueue *streams, GHashTable *);
 void sdp_free(GQueue *sessions);