gtpie_gettlv(): fix return value on specific error.neels/refactor

Make gtpie_gettlv() return an error if gtpie_getie() returned an error.
Previously, openggsn would fail to complain about certain missing elements.

Technically, a missing IE could be detectable from the *length value, but the
code in gtp.c relies on the return value to detect missing elements, which did
not work prior to this commit. For example:

if (gtpie_gettlv(ie, GTPIE_EUA, 0, &pdp->eua.l,
		 &pdp->eua.v, sizeof(pdp->eua.v))) {
	gsn->missing++;
	GTP_LOGPKG(LOGL_ERROR, peer, pack,
		    len, "Missing mandatory information field\n");
	return gtp_create_pdp_resp(gsn, version, pdp,
				   GTPCAUSE_MAN_IE_MISSING);
}

If an EUA were missing in this code path, openggsn would fail to issue an error
message. Since pdp and hence pdp->eua.l is initialized as all-zero, it would
probably not do much harm besides failing to issue an error.

I haven't checked all callers though.

1 files changed, 8 insertions, 7 deletions

diff --git a/gtp/gtpie.c b/gtp/gtpie.c
index d70db6a..bbb9537 100644
--- a/gtp/gtpie.c
+++ b/gtp/gtpie.c
@@ -135,13 +135,14 @@ int gtpie_gettlv(union gtpie_member *ie[], int type, int instance,
 {
 	int ien;
 	ien = gtpie_getie(ie, type, instance);
-	if (ien >= 0) {
-		*length = ntoh16(ie[ien]->tlv.l);
-		if (*length <= size)
-			memcpy(dst, ie[ien]->tlv.v, *length);
-		else
-			return EOF;
-	}
+	if (ien < 0)
+		return EOF;
+
+	*length = ntoh16(ie[ien]->tlv.l);
+	if (*length > size)
+		return EOF;
+
+	memcpy(dst, ie[ien]->tlv.v, *length);
 	return 0;
 }