gtphub: add first bits of GRX ares

For the resolving function, change the function signature to return a
gtphub_peer_port. In consequence, publish two functions concerned with
gtphub_peer_port instances for use in test and gtphub_ext.c.

Add GGSN resolution queue, callback and cache. Simple implementation: if an
SGSN asks for a GGSN, it will first get no answer, and I hope it will ask again
once the GGSN is in the cache.

Within gtphub_ext.c, have a dummy sgsn struct, as the sgsn_ares code currently
depends on it (half the functions pass an sgsn instance pointer around, but the
other half use the global one).

In the unit tests, wrap away the ares initialization so that they can work
without a DNS server around. The netcat test breaks because of this, will
remove it.

Using sgsn_ares, implement the gtphub_resolve_ggsn_addr() function, I hope:
untested.

Minor cosmetics just to see if you're paying attention... ;)

Sponsored-by: On-Waves ehi

1 files changed, 5 insertions, 0 deletions

diff --git a/openbsc/src/gprs/sgsn_vty.c b/openbsc/src/gprs/sgsn_vty.c
index 3a73c9f55..3f6116393 100644
--- a/openbsc/src/gprs/sgsn_vty.c
+++ b/openbsc/src/gprs/sgsn_vty.c
@@ -110,6 +110,11 @@ DECLARE_TIMER(3397, "Wait for DEACT AA PDP CTX ACK timer (s)")
 
 
 #define GSM48_MAX_APN_LEN	102	/* 10.5.6.1 */
+/* TODO: consolidate with gprs_apn_to_str(). */
+/** Copy apn to a static buffer, replacing the length octets in apn_enc with '.'
+ * and terminating with a '\0'. Return the static buffer.
+ * len: the length of the encoded APN (which has no terminating zero).
+ */
 static char *gprs_apn2str(uint8_t *apn, unsigned int len)
 {
 	static char apnbuf[GSM48_MAX_APN_LEN+1];