From 95308596540b0733a43d9db5dc6ab0c4f5e2d08f Mon Sep 17 00:00:00 2001
From: Max <msuraev@sysmocom.de>
Date: Tue, 24 Oct 2017 15:54:28 +0200
Subject: [PATCH] GPRS: clarify ip/frgre union use

* add comment about underlying assumption that structs in ip/frgre union
  members in gprs_nsvc struct have the same memory layout
* remove such assumption from gprs_ns_ll_str()
* use gprs_ns_ll_str() for NSE dump

Change-Id: Idcb912b7b3f7460fd2b058e16650c0bde8f757ee
---
 include/osmocom/gprs/gprs_ns.h |  2 ++
 src/gb/gprs_ns.c               | 18 +++++++++++++++---
 src/gb/gprs_ns_vty.c           | 11 +++++------
 3 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/include/osmocom/gprs/gprs_ns.h b/include/osmocom/gprs/gprs_ns.h
index 2d2f86ed6..4fb9f5846 100644
--- a/include/osmocom/gprs/gprs_ns.h
+++ b/include/osmocom/gprs/gprs_ns.h
@@ -140,6 +140,8 @@ struct gprs_nsvc {
 	/*! which link-layer are we based on? */
 	enum gprs_ns_ll ll;
 
+	/*! make sure to always keep bts_addr as first struct member to not break the assumption
+	  that those structs are similar */
 	union {
 		struct {
 			struct sockaddr_in bts_addr;
diff --git a/src/gb/gprs_ns.c b/src/gb/gprs_ns.c
index 2d062cf23..18d43ccc2 100644
--- a/src/gb/gprs_ns.c
+++ b/src/gb/gprs_ns.c
@@ -1173,9 +1173,21 @@ int gprs_ns_rcvmsg(struct gprs_ns_inst *nsi, struct msgb *msg,
 const char *gprs_ns_ll_str(struct gprs_nsvc *nsvc)
 {
 	static char buf[80];
-	snprintf(buf, sizeof(buf), "%s:%u",
-		 inet_ntoa(nsvc->ip.bts_addr.sin_addr),
-		 osmo_ntohs(nsvc->ip.bts_addr.sin_port));
+
+	switch(nsvc->ll) {
+	case GPRS_NS_LL_UDP:
+		snprintf(buf, sizeof(buf), "%s:%u",
+			 inet_ntoa(nsvc->ip.bts_addr.sin_addr), osmo_ntohs(nsvc->ip.bts_addr.sin_port));
+		break;
+	case GPRS_NS_LL_FR_GRE:
+		snprintf(buf, sizeof(buf), "%s:%u",
+			 inet_ntoa(nsvc->frgre.bts_addr.sin_addr), osmo_ntohs(nsvc->frgre.bts_addr.sin_port));
+		break;
+	default:
+		buf[0] = '\0';
+		break;
+	}
+
 	buf[sizeof(buf) - 1] = '\0';
 
 	return buf;
diff --git a/src/gb/gprs_ns_vty.c b/src/gb/gprs_ns_vty.c
index 317a6a10a..4ed4fefb1 100644
--- a/src/gb/gprs_ns_vty.c
+++ b/src/gb/gprs_ns_vty.c
@@ -165,12 +165,11 @@ static void dump_nse(struct vty *vty, struct gprs_nsvc *nsvc, int stats)
 		nsvc->remote_end_is_sgsn ? "SGSN" : "BSS",
 		NS_DESC_A(nsvc->remote_state),
 		NS_DESC_B(nsvc->remote_state));
-	if (nsvc->ll == GPRS_NS_LL_UDP || nsvc->ll == GPRS_NS_LL_FR_GRE)
-		vty_out(vty, ", %s %15s:%u",
-			nsvc->ll == GPRS_NS_LL_UDP ? "UDP   " : "FR-GRE",
-			inet_ntoa(nsvc->ip.bts_addr.sin_addr),
-			osmo_ntohs(nsvc->ip.bts_addr.sin_port));
-	vty_out(vty, "%s", VTY_NEWLINE);
+
+	vty_out(vty, ", %s %s%s",
+		nsvc->ll == GPRS_NS_LL_UDP ? "UDP   " : "FR-GRE",
+		gprs_ns_ll_str(nsvc), VTY_NEWLINE);
+
 	if (stats) {
 		vty_out_rate_ctr_group(vty, " ", nsvc->ctrg);
 		vty_out_stat_item_group(vty, " ", nsvc->statg);