Hi openbsc, the following patch series adds a GTP hub program (maturity level: proof-of-concept). Its aim is related to the recent addition of OAP: it will allow routing multiple SGSNs through one GTP server hub (proxy). The program so far forwards UDP packets to and from hardcoded ports, and logs validity of GTP headers passing through. I think this a good time to do a review cycle and merge to master, before adding the interesting stuff. What will follow: decode GTP body, map/separate PDP contexts across clients and servers, replace TEIs. To do that without reinventing the GTP wheel, I may need to separate data parsing from send/recv in openggsn. There are also some bits that should probably be moved out (to where I copied it from) and the API there changed (so that I can use it here without copying). Those are clearly marked with todo comments. Thanks for your review! ~Neels