diff --git a/daemon/bencode.h b/daemon/bencode.h
index 91f7ed95e..871a805a7 100644
--- a/daemon/bencode.h
+++ b/daemon/bencode.h
@@ -122,6 +122,10 @@ bencode_item_t *bencode_string_len(bencode_buffer_t *buf, const char *s, int len
  * to bencode_string_len(). */
 static inline bencode_item_t *bencode_string(bencode_buffer_t *buf, const char *s);
 
+/* Convenience function to compare a string object to a regular C string. Returns 2 if object
+ * isn't a string object, otherwise returns according to strcmp(). */
+static inline int bencode_strcmp(bencode_item_t *a, const char *b);
+
 /* Creates a new byte-string object from a "str" object. The string does not have to be null-
  * terminated. */
 static inline bencode_item_t *bencode_str(bencode_buffer_t *buf, const str *s);
@@ -360,5 +364,16 @@ static inline str *bencode_collapse_str(bencode_item_t *root, str *out) {
 	out->s = bencode_collapse(root, &out->len);
 	return out;
 }
+static inline int bencode_strcmp(bencode_item_t *a, const char *b) {
+	int len;
+	if (a->type != BENCODE_STRING)
+		return 2;
+	len = strlen(b);
+	if (a->iov[1].iov_len < len)
+		return -1;
+	if (a->iov[1].iov_len > len)
+		return 1;
+	return memcmp(a->iov[1].iov_base, b, len);
+}
 
 #endif
diff --git a/daemon/call.c b/daemon/call.c
index 24b74292b..c03a0b406 100644
--- a/daemon/call.c
+++ b/daemon/call.c
@@ -45,10 +45,6 @@ static __thread const str *log_info;
 
 
 /* also serves as array index for callstream->peers[] */
-enum opmode {
-	OP_OFFER = 0,
-	OP_ANSWER = 1,
-};
 struct iterator_helper {
 	GSList			*del;
 	struct streamrelay	*ports[0x10000];
@@ -1174,7 +1170,7 @@ static void callstream_free(void *ptr) {
 }
 
 /* called with call->lock held */
-static int call_streams(struct call *c, GQueue *s, const str *tag, enum opmode opmode) {
+static int call_streams(struct call *c, GQueue *s, const str *tag, enum call_opmode opmode) {
 	GQueue *q;
 	GList *i, *l;
 	struct stream_input *t;
@@ -1220,7 +1216,7 @@ static int call_streams(struct call *c, GQueue *s, const str *tag, enum opmode o
 
 found:
 		/* cs_o remains locked if set */
-		if (!opmode) {	/* request */
+		if (opmode == OP_OFFER) {
 			DBG("creating new callstream");
 
 			cs = callstream_new(c, t->stream.num);
@@ -1507,18 +1503,18 @@ int call_stream_address(GString *o, struct peer *p, enum stream_address_format f
 
 
 
-static str *streams_print(GQueue *s, int rawnum, enum opmode opmode, const char *prefix, enum stream_address_format format) {
+static str *streams_print(GQueue *s, int num, enum call_opmode opmode, const char *prefix, enum stream_address_format format) {
 	GString *o;
-	int i, num, off;
+	int i, off;
 	GList *l;
 	struct callstream *t;
 	struct streamrelay *x;
 	int af;
 
-	num = abs(rawnum);
 	off = opmode; /* 0 or 1 */
 	if (num < 0)
 		off ^= 1; /* 1 or 0 */
+	num = abs(num);
 
 	o = g_string_new_str();
 	if (prefix)
@@ -1635,7 +1631,7 @@ static struct call *call_get(const str *callid, const str *viabranch, struct cal
 }
 
 /* returns call with lock held, or possibly NULL iff opmode == OP_ANSWER */
-static struct call *call_get_opmode(const str *callid, const str *viabranch, struct callmaster *m, enum opmode opmode) {
+static struct call *call_get_opmode(const str *callid, const str *viabranch, struct callmaster *m, enum call_opmode opmode) {
 	if (opmode == OP_OFFER)
 		return call_get_or_create(callid, viabranch, m);
 	return call_get(callid, viabranch, m);
@@ -1686,7 +1682,7 @@ fail:
 	return -1;
 }
 
-static str *call_update_lookup_udp(char **out, struct callmaster *m, enum opmode opmode, int tagidx) {
+static str *call_update_lookup_udp(char **out, struct callmaster *m, enum call_opmode opmode, int tagidx) {
 	struct call *c;
 	GQueue q = G_QUEUE_INIT;
 	struct stream_input st;
@@ -1738,7 +1734,7 @@ str *call_lookup_udp(char **out, struct callmaster *m) {
 	return call_update_lookup_udp(out, m, OP_ANSWER, RE_UDP_UL_TOTAG);
 }
 
-static str *call_request_lookup(char **out, struct callmaster *m, enum opmode opmode, const char *tagstr) {
+static str *call_request_lookup(char **out, struct callmaster *m, enum call_opmode opmode, const char *tagstr) {
 	struct call *c;
 	GQueue s = G_QUEUE_INIT;
 	int num;
@@ -2091,6 +2087,53 @@ struct callstream *callstream_new(struct call *ca, int num) {
 }
 
 
+static void call_ng_process_flags(struct sdp_ng_flags *out, GQueue *streams, bencode_item_t *input) {
+	bencode_item_t *list, *it;
+	struct stream_input *si;
+	int diridx;
+	enum stream_direction dirs[2];
+	GList *gl;
+
+	ZERO(*out);
+	ZERO(dirs);
+
+	if ((list = bencode_dictionary_get_expect(input, "flags", BENCODE_LIST))) {
+		for (it = list->child; it; it = it->sibling) {
+			if (!bencode_strcmp(it, "trust-address")) /* XXX not implemented */
+				out->trust_address = 1;
+			else if (!bencode_strcmp(it, "symmetric"))
+				out->symmetric = 1;
+			else if (!bencode_strcmp(it, "asymmetric"))
+				out->asymmetric = 1;
+		}
+	}
+
+	if ((list = bencode_dictionary_get_expect(input, "replace", BENCODE_LIST))) {
+		for (it = list->child; it; it = it->sibling) {
+			if (!bencode_strcmp(it, "origin"))
+				out->replace_origin = 1;
+			else if (!bencode_strcmp(it, "session-connection"))
+				out->replace_sess_conn = 1;
+		}
+	}
+
+	diridx = 0;
+	if ((list = bencode_dictionary_get_expect(input, "direction", BENCODE_LIST))) {
+		for (it = list->child; it && diridx < 2; it = it->sibling) {
+			if (!bencode_strcmp(it, "internal"))
+				dirs[diridx++] = DIR_INTERNAL;
+			else if (!bencode_strcmp(it, "external"))
+				dirs[diridx++] = DIR_INTERNAL;
+		}
+
+		for (gl = streams->head; gl; gl = gl->next) {
+			si = gl->data;
+			si->direction[0] = dirs[0];
+			si->direction[1] = dirs[1];
+		}
+	}
+}
+
 const char *call_offer(bencode_item_t *input, struct callmaster *m, bencode_item_t *output) {
 	str sdp, fromtag, viabranch, callid, *sdp_new;
 	char *errstr;
@@ -2098,6 +2141,7 @@ const char *call_offer(bencode_item_t *input, struct callmaster *m, bencode_item
 	GQueue streams = G_QUEUE_INIT;
 	struct call *call;
 	int num;
+	struct sdp_ng_flags flags;
 
 	if (!bencode_dictionary_get_str(input, "sdp", &sdp))
 		return "No SDP body in message";
@@ -2108,8 +2152,6 @@ const char *call_offer(bencode_item_t *input, struct callmaster *m, bencode_item
 	bencode_dictionary_get_str(input, "via-branch", &viabranch);
 	log_info = &viabranch;
 
-	/* XXX get rid of "direction" and use "desired_family" as intended? */
-
 	if (sdp_parse(&sdp, &parsed))
 		return "Failed to parse SDP";
 
@@ -2117,11 +2159,13 @@ const char *call_offer(bencode_item_t *input, struct callmaster *m, bencode_item
 	if (sdp_streams(&parsed, &streams))
 		goto out;
 
+	call_ng_process_flags(&flags, &streams, input);
+
 	call = call_get_or_create(&callid, &viabranch, m);
 	log_info = &viabranch;
 
 	num = call_streams(call, &streams, &fromtag, OP_OFFER);
-	sdp_new = sdp_replace(&sdp, &parsed, call, abs(num), (num >= 0) ? 0 : 1);
+	sdp_new = sdp_replace(&sdp, &parsed, call, num, OP_OFFER, &flags);
 
 	mutex_unlock(&call->lock);
 	obj_put(call);
diff --git a/daemon/call.h b/daemon/call.h
index b0ca4827c..c881b2eda 100644
--- a/daemon/call.h
+++ b/daemon/call.h
@@ -35,6 +35,15 @@ enum stream_address_format {
 	SAF_UDP,
 	SAF_NG,
 };
+enum stream_direction {
+	DIR_UNKNOWN = 0,
+	DIR_INTERNAL,
+	DIR_EXTERNAL,
+};
+enum call_opmode {
+	OP_OFFER = 0,
+	OP_ANSWER = 1,
+};
 
 struct stats {
 	u_int64_t			packets;
@@ -49,11 +58,7 @@ struct stream {
 };
 struct stream_input {
 	struct stream		stream;
-	enum {
-		DIR_UNKNOWN = 0,
-		DIR_INTERNAL,
-		DIR_EXTERNAL,
-	}			direction[2];
+	enum stream_direction	direction[2];
 };
 struct streamrelay {
 	int			fd;
diff --git a/daemon/sdp.c b/daemon/sdp.c
index c27ea6142..5fb17d2d6 100644
--- a/daemon/sdp.c
+++ b/daemon/sdp.c
@@ -452,11 +452,17 @@ static void chopper_destroy(struct string_chopper *chop) {
 /* XXX use port numbers as index */
 /* XXX get rid of num/off parameters? */
 /* XXX use iovec based rewriting */
-str *sdp_replace(str *body, GQueue *sessions, struct call *call, int num, int off) {
+str *sdp_replace(str *body, GQueue *sessions, struct call *call, int num, enum call_opmode opmode, struct sdp_ng_flags *flags) {
 	struct sdp_session *session;
 	struct sdp_media *media;
 	GList *l, *k, *m;
 	struct string_chopper chop;
+	int off;
+
+	off = opmode;
+	if (num < 0)
+		off ^= 1;
+	num = abs(num);
 
 	chopper_init(&chop, body);
 	m = call->callstreams->head;
@@ -464,7 +470,7 @@ str *sdp_replace(str *body, GQueue *sessions, struct call *call, int num, int of
 	for (l = sessions->head; l; l = l->next) {
 		session = l->data;
 
-		if (session->origin.parsed) {
+		if (session->origin.parsed && flags->replace_origin) {
 			if (replace_network_address(&chop, &session->origin.address, m, off))
 				goto error;
 		}
@@ -480,7 +486,7 @@ str *sdp_replace(str *body, GQueue *sessions, struct call *call, int num, int of
 			if (replace_port(&chop, &media->port, m, off))
 				goto error;
 
-			if (media->connection.parsed) {
+			if (media->connection.parsed && flags->replace_sess_conn) {
 				if (replace_network_address(&chop, &media->connection.address, m, off))
 					goto error;
 			}
diff --git a/daemon/sdp.h b/daemon/sdp.h
index 55f435c62..6aa98a2ca 100644
--- a/daemon/sdp.h
+++ b/daemon/sdp.h
@@ -5,9 +5,19 @@
 #include "str.h"
 #include "call.h"
 
+
+struct sdp_ng_flags {
+	int desired_family[2];
+	int asymmetric:1,
+	    symmetric:1,
+	    trust_address:1,
+	    replace_origin:1,
+	    replace_sess_conn:1;
+};
+
 int sdp_parse(str *body, GQueue *sessions);
 int sdp_streams(const GQueue *sessions, GQueue *streams);
 void sdp_free(GQueue *sessions);
-str *sdp_replace(str *body, GQueue *sessions, struct call *call, int num, int off);
+str *sdp_replace(str *body, GQueue *sessions, struct call *call, int num, enum call_opmode, struct sdp_ng_flags *);
 
 #endif
diff --git a/daemon/str.h b/daemon/str.h
index c3cee3932..7cf5613b1 100644
--- a/daemon/str.h
+++ b/daemon/str.h
@@ -35,6 +35,8 @@ static inline char *str_chr(const str *s, int c);
 static inline str *str_chr_str(str *out, const str *s, int c);
 /* compares a str to a regular string */
 static inline int str_cmp(const str *a, const char *b);
+/* compares a str to a non-null-terminated string */
+static inline int str_cmp_len(const str *a, const char *b, int len);
 /* compares two str objects */
 static inline int str_cmp_str(const str *a, const str *b);
 /* compares two str objects, allows either to be NULL */
@@ -80,8 +82,7 @@ static inline str *str_chr_str(str *out, const str *s, int c) {
 	out->len = out->s ? (s->len - (out->s - s->s)) : 0;
 	return out;
 }
-static inline int str_cmp(const str *a, const char *b) {
-	int l = strlen(b);
+static inline int str_cmp_len(const str *a, const char *b, int l) {
 	if (a->len < l)
 		return -1;
 	if (a->len > l)
@@ -90,6 +91,9 @@ static inline int str_cmp(const str *a, const char *b) {
 		return 0;
 	return memcmp(a->s, b, l);
 }
+static inline int str_cmp(const str *a, const char *b) {
+	return str_cmp_len(a, b, strlen(b));
+}
 static inline int str_cmp_str(const str *a, const str *b) {
 	if (a->len < b->len)
 		return -1;