nat: Remove the broken empty line check, follow \n vs \r\n of input

Instead of checking the token for NULL we need to check if running
was set to null. Look at the data of the token and check if the line
was ending with a \r\n or \n and then when rewriting a line use that
line ending as well. Add a new test for that.

2 files changed, 23 insertions, 9 deletions

diff --git a/openbsc/src/nat/bsc_mgcp_utils.c b/openbsc/src/nat/bsc_mgcp_utils.c
index 164b6f64c..2b28305a8 100644
--- a/openbsc/src/nat/bsc_mgcp_utils.c
+++ b/openbsc/src/nat/bsc_mgcp_utils.c
@@ -277,21 +277,24 @@ struct msgb *bsc_mgcp_rewrite(char *input, int length, const char *ip, int port)
 
 	running = input;
 	output->l2h = output->data;
-	for (token = strsep(&running, "\n"); token; token = strsep(&running, "\n")) {
+	for (token = strsep(&running, "\n"); running; token = strsep(&running, "\n")) {
 		int len = strlen(token);
-
-		/* ignore completely empty lines for now */
-		if (len == 0)
-			continue;
+		int cr = len > 0 && token[len - 1] == '\r';
 
 		if (strncmp(ip_str, token, (sizeof ip_str) - 1) == 0) {
 			output->l3h = msgb_put(output, strlen(ip_str));
 			memcpy(output->l3h, ip_str, strlen(ip_str));
 			output->l3h = msgb_put(output, strlen(ip));
 			memcpy(output->l3h, ip, strlen(ip));
-			output->l3h = msgb_put(output, 2);
-			output->l3h[0] = '\r';
-			output->l3h[1] = '\n';
+
+			if (cr) {
+				output->l3h = msgb_put(output, 2);
+				output->l3h[0] = '\r';
+				output->l3h[1] = '\n';
+			} else {
+				output->l3h = msgb_put(output, 1);
+				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) {
@@ -300,7 +303,8 @@ struct msgb *bsc_mgcp_rewrite(char *input, int length, const char *ip, int port)
 				return NULL;
 			}
 
-			snprintf(buf, sizeof(buf)-1, "m=audio %d RTP/AVP %d\r\n", port, payload);
+			snprintf(buf, sizeof(buf)-1, "m=audio %d RTP/AVP %d%s",
+				 port, payload, cr ? "\r\n" : "\n");
 			buf[sizeof(buf)-1] = '\0';
 
 			output->l3h = msgb_put(output, strlen(buf));
diff --git a/openbsc/tests/bsc-nat/bsc_data.c b/openbsc/tests/bsc-nat/bsc_data.c
index 28d506466..34242db8c 100644
--- a/openbsc/tests/bsc-nat/bsc_data.c
+++ b/openbsc/tests/bsc-nat/bsc_data.c
@@ -109,6 +109,10 @@ static const char mdcx_patched[] = " MDCX 23330829 8@mgw MGCP 1.0\r\nC: 394b0439
 static const char mdcx_resp[] = "200 23330829\r\n\r\nv=0\r\nc=IN IP4 172.16.18.2\r\nm=audio 4002 RTP/AVP 98\r\na=rtpmap:98 AMR/8000\r\n";
 static const char mdcx_resp_patched[] = "200 23330829\r\n\r\nv=0\r\nc=IN IP4 10.0.0.23\r\nm=audio 5555 RTP/AVP 98\r\na=rtpmap:98 AMR/8000\r\n";
 
+/* different line ending */
+static const char mdcx_resp2[] = "200 33330829\n\nv=0\nc=IN IP4 172.16.18.2\nm=audio 4002 RTP/AVP 98\na=rtpmap:98 AMR/8000\n";
+static const char mdcx_resp_patched2[] = "200 33330829\n\nv=0\nc=IN IP4 10.0.0.23\nm=audio 5555 RTP/AVP 98\na=rtpmap:98 AMR/8000\n";
+
 struct mgcp_patch_test {
 	const char *orig;
 	const char *patch;
@@ -141,4 +145,10 @@ static const struct mgcp_patch_test mgcp_messages[] = {
 		.ip = "10.0.0.23",
 		.port = 5555,
 	},
+	{
+		.orig = mdcx_resp2,
+		.patch = mdcx_resp_patched2,
+		.ip = "10.0.0.23",
+		.port = 5555,
+	},
 };