xua_msg: Add xua_msg*_get_str() to obtain string IE

We copy the contents to a static thread-local buffer to ensure
zero termination of the string received by a remote entity.

Change-Id: I8cbb7aeaf0cb64db0ce01c21e5fca9ab3cd932b6

2 files changed, 25 insertions, 0 deletions

diff --git a/include/osmocom/sigtran/xua_msg.h b/include/osmocom/sigtran/xua_msg.h
index a2cdbf2..329ba96 100644
--- a/include/osmocom/sigtran/xua_msg.h
+++ b/include/osmocom/sigtran/xua_msg.h
@@ -91,6 +91,8 @@ int msgb_t16l16vp_put_u32(struct msgb *msg, uint16_t tag, uint32_t val);
 int xua_msg_add_u32(struct xua_msg *xua, uint16_t iei, uint32_t val);
 uint32_t xua_msg_part_get_u32(const struct xua_msg_part *part);
 uint32_t xua_msg_get_u32(const struct xua_msg *xua, uint16_t iei);
+const char *xua_msg_part_get_str(const struct xua_msg_part *part);
+const char *xua_msg_get_str(const struct xua_msg *xua, uint16_t iei);
 void xua_part_add_gt(struct msgb *msg, const struct osmo_sccp_gt *gt);
 int xua_msg_add_sccp_addr(struct xua_msg *xua, uint16_t iei, const struct osmo_sccp_addr *addr);
 
diff --git a/src/xua_msg.c b/src/xua_msg.c
index 79c358c..42c580d 100644
--- a/src/xua_msg.c
+++ b/src/xua_msg.c
@@ -297,6 +297,29 @@ uint32_t xua_msg_get_u32(const struct xua_msg *xua, uint16_t iei)
 	return xua_msg_part_get_u32(part);
 }
 
+const char *xua_msg_part_get_str(const struct xua_msg_part *part)
+{
+	static char __thread buf[256];
+
+	if (part->len == 0)
+		return "";
+	/* RFC3868 3.9.4: Length of the INFO String parameter is from 0 to 255 octets */
+	if (part->len > 255)
+		return "<invalid-string-len>";
+
+	memcpy(buf, part->dat, part->len);
+	buf[part->len] = '\0';
+	return buf;
+}
+
+const char *xua_msg_get_str(const struct xua_msg *xua, uint16_t iei)
+{
+	struct xua_msg_part *part = xua_msg_find_tag(xua, iei);
+	if (!part)
+		return NULL;
+	return xua_msg_part_get_str(part);
+}
+
 void xua_part_add_gt(struct msgb *msg, const struct osmo_sccp_gt *gt)
 {
 	uint16_t *len_ptr;