gbproxy: Add SGSN pooling support

Change-Id: I58b9f55065f6bd43450e4b07cffe7ba132b1fd9b
Related: OS#4472
diff --git a/include/osmocom/sgsn/gb_proxy.h b/include/osmocom/sgsn/gb_proxy.h
index 46decc0..8654d10 100644
--- a/include/osmocom/sgsn/gb_proxy.h
+++ b/include/osmocom/sgsn/gb_proxy.h
@@ -229,5 +229,7 @@
 struct gbproxy_sgsn *gbproxy_sgsn_by_nsei(struct gbproxy_config *cfg, uint16_t nsei);
 struct gbproxy_sgsn *gbproxy_sgsn_by_nsei_or_new(struct gbproxy_config *cfg, uint16_t nsei);
 struct gbproxy_sgsn *gbproxy_sgsn_by_nri(struct gbproxy_config *cfg, uint16_t nri, bool *null_nri);
+struct gbproxy_sgsn *gbproxy_sgsn_by_tlli(struct gbproxy_config *cfg, struct gbproxy_sgsn *sgsn_avoid,
+					  uint32_t tlli);
 
 #endif