nat: Inject a a=fmtp:%d to force the right AMR code
This assumes that AMR is used and/or the mode-set is ignored for other
codecs by the remote end.
diff --git a/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c b/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c
index 668ddd6..d78dc91 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c
@@ -563,12 +563,18 @@
static const char *ip_str = "c=IN IP4 ";
static const char *aud_str = "m=audio ";
+ static const char *fmt_str = "a=fmtp: ";
char buf[128];
char *running, *token;
struct msgb *output;
- if (length > 4096 - 128) {
+ /* keep state to add the a=fmtp line */
+ int found_fmtp = 0;
+ int payload = -1;
+ int cr = 1;
+
+ if (length > 4096 - 256) {
LOGP(DMGCP, LOGL_ERROR, "Input is too long.\n");
return NULL;
}
@@ -584,7 +590,7 @@
output->l3h = output->l2h;
for (token = strsep(&running, "\n"); running; token = strsep(&running, "\n")) {
int len = strlen(token);
- int cr = len > 0 && token[len - 1] == '\r';
+ cr = len > 0 && token[len - 1] == '\r';
if (strncmp(crcx_str, token, (sizeof crcx_str) - 1) == 0) {
patch_mgcp(output, "CRCX", token, endpoint, len, cr);
@@ -607,7 +613,6 @@
output->l3h[0] = '\n';
}
} else if (strncmp(aud_str, token, (sizeof aud_str) - 1) == 0) {
- int payload;
if (sscanf(token, "m=audio %*d RTP/AVP %d", &payload) != 1) {
LOGP(DMGCP, LOGL_ERROR, "Could not parsed audio line.\n");
msgb_free(output);
@@ -620,13 +625,29 @@
output->l3h = msgb_put(output, strlen(buf));
memcpy(output->l3h, buf, strlen(buf));
+ } else if (strncmp(fmt_str, token, (sizeof fmt_str) - 1) == 0) {
+ found_fmtp = 1;
+ goto copy;
} else {
+copy:
output->l3h = msgb_put(output, len + 1);
memcpy(output->l3h, token, len);
output->l3h[len] = '\n';
}
}
+ /*
+ * the above code made sure that we have 128 bytes lefts. So we can
+ * safely append another line.
+ */
+ if (!found_fmtp && payload != -1) {
+ snprintf(buf, sizeof(buf) - 1, "a=fmtp:%d mode-set=2%s",
+ payload, cr ? "\r\n" : "\n");
+ buf[sizeof(buf) - 1] = '\0';
+ output->l3h = msgb_put(output, strlen(buf));
+ memcpy(output->l3h, buf, strlen(buf));
+ }
+
return output;
}