Payload protocol identifier is not specified in SCTP about srsran_project HOT 8 CLOSED

[2023-03-07T09:17:36.068790] [AMF] [sctp   ] [debug] SCTP Association Change event received
[2023-03-07T09:17:36.068810] [AMF] [sctp   ] [debug] Add new association with id (17812)
[2023-03-07T09:17:36.068850] [AMF] [ngap   ] [debug] Ready to handle new NGAP SCTP association request (id 17812)
[2023-03-07T09:17:36.068853] [AMF] [ngap   ] [debug] Create a new gNB context with assoc_id (17812)
[2023-03-07T09:17:36.070346] [AMF] [sctp   ] [error] Received data from peer with unsolicited PPID (0), 
expecting (60)

commit ec07389145175e86f9468363e67e934ca3ff1e44 (HEAD -> sctp_ppid, origin/sctp_ppid)
Author: Pedro Alvarez <[email protected]>
Date:   Tue Mar 7 18:48:52 2023 +0000

    sctp: fix NGAP ppid

diff --git a/apps/gnb/gnb.cpp b/apps/gnb/gnb.cpp
index ab5b8a00b..fe1a4b295 100644
--- a/apps/gnb/gnb.cpp
+++ b/apps/gnb/gnb.cpp
@@ -92,6 +92,7 @@ static void compute_derived_args(const gnb_appconfig& gnb_params)
   ngap_nw_config.connect_address = gnb_params.amf_cfg.ip_addr;
   ngap_nw_config.connect_port    = gnb_params.amf_cfg.port;
   ngap_nw_config.bind_address    = gnb_params.amf_cfg.bind_addr;
+  ngap_nw_config.ppid            = NGAP_PPID;
 }
 
 namespace {
diff --git a/include/srsran/gateways/sctp_network_gateway.h b/include/srsran/gateways/sctp_network_gateway.h
index 2b897c44e..fba94e626 100644
--- a/include/srsran/gateways/sctp_network_gateway.h
+++ b/include/srsran/gateways/sctp_network_gateway.h
@@ -19,10 +19,13 @@
 
 namespace srsran {
 
+constexpr uint16_t NGAP_PPID = 60; // NGAP PPID, see TS 38.412, section 7.
+
 /// \brief Configuration for SCTP network gateway
 struct sctp_network_gateway_config : common_network_gateway_config {
   std::string connect_address;
   int         connect_port = 0;
+  int         ppid         = 0; /// the Payload Protocol Identifier
   // TODO add SCTP specific options
 };
 
diff --git a/lib/gateways/sctp_network_gateway_impl.cpp b/lib/gateways/sctp_network_gateway_impl.cpp
index 48e374660..0cb6c0cd1 100644
--- a/lib/gateways/sctp_network_gateway_impl.cpp
+++ b/lib/gateways/sctp_network_gateway_impl.cpp
@@ -546,7 +546,7 @@ void sctp_network_gateway_impl::handle_pdu(const byte_buffer& pdu)
                                 pdu_span.size_bytes(),
                                 (struct sockaddr*)&server_addr,
                                 server_addrlen,
-                                ppi,
+                                htonl(config.ppid),
                                 0,
                                 stream_no,
                                 0,
diff --git a/lib/gateways/sctp_network_gateway_impl.h b/lib/gateways/sctp_network_gateway_impl.h
index 45df3cbe2..4d1b594d6 100644
--- a/lib/gateways/sctp_network_gateway_impl.h
+++ b/lib/gateways/sctp_network_gateway_impl.h
@@ -90,7 +90,6 @@ private:
   int                     server_ai_socktype = 0;
   int                     server_ai_protocol = 0;
 
-  unsigned ppi       = 0; /// the Payload Protocol Identifier (e.g. 18 for S1AP)
   unsigned stream_no = 0; /// the stream number to use for sending
 };