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Add feature to provide custom GTP-U (S1) address to be advertised inside S1AP messages

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This feature is useful in scenarios where eNB is behind a NAT and EPC on public cloud
Since eNB's GTP-U can only bind to IP address visible in it's host (usually a private IP beind a NAT), it advertises the same to UE in S1AP message
resulting in traffic from EPC to eNB (DL traffic) not able to reach eNB. This commit solves this issue by providing a means to advertise a different IP address than the one GTP-U UDP socket is bound to.
This IP is usually advertised in InitialContextSetupResponse and E-RABSetupResponse.

In order to make use of this feature, use the following parameter in enb.conf

Example:

gtp_advertise_addr = 213.61.141.82
master
herlesupreeth 4 years ago committed by Andre Puschmann
parent aff9091ad3
commit 0f06ec0d9c
4 changed files with 34 additions and 23 deletions
Show Stats Download Patch File Download Diff File

1
lib/include/srsran/interfaces/enb_s1ap_interfaces.h
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@ -26,6 +26,7 @@ struct s1ap_args_t {
uint16_t mnc; // BCD-coded with 0xF filler
std::string mme_addr;
std::string gtp_bind_addr;
std::string gtp_advertise_addr;
std::string s1c_bind_addr;
std::string enb_name;
};

19
srsenb/enb.conf.example
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@ -5,15 +5,16 @@
#####################################################################
# eNB configuration
#
# enb_id: 20-bit eNB identifier.
# mcc: Mobile Country Code
# mnc: Mobile Network Code
# mme_addr: IP address of MME for S1 connnection
# gtp_bind_addr: Local IP address to bind for GTP connection
# s1c_bind_addr: Local IP address to bind for S1AP connection
# n_prb: Number of Physical Resource Blocks (6,15,25,50,75,100)
# tm: Transmission mode 1-4 (TM1 default)
# nof_ports: Number of Tx ports (1 port default, set to 2 for TM2/3/4)
# enb_id: 20-bit eNB identifier.
# mcc: Mobile Country Code
# mnc: Mobile Network Code
# mme_addr: IP address of MME for S1 connnection
# gtp_bind_addr: Local IP address to bind for GTP connection
# gtp_advertise_addr: IP address of eNB to advertise for DL GTP-U Traffic
# s1c_bind_addr: Local IP address to bind for S1AP connection
# n_prb: Number of Physical Resource Blocks (6,15,25,50,75,100)
# tm: Transmission mode 1-4 (TM1 default)
# nof_ports: Number of Tx ports (1 port default, set to 2 for TM2/3/4)
#
#####################################################################
[enb]

25
srsenb/src/main.cc
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@ -64,18 +64,19 @@ void parse_args(all_args_t* args, int argc, char* argv[])
bpo::options_description common("Configuration options");
common.add_options()
("enb.stack", bpo::value<string>(&args->stack.type)->default_value("lte"), "Type of the upper stack [lte, nr]")
("enb.enb_id", bpo::value<string>(&enb_id)->default_value("0x0"), "eNodeB ID")
("enb.name", bpo::value<string>(&args->stack.s1ap.enb_name)->default_value("srsenb01"), "eNodeB Name")
("enb.mcc", bpo::value<string>(&mcc)->default_value("001"), "Mobile Country Code")
("enb.mnc", bpo::value<string>(&mnc)->default_value("01"), "Mobile Network Code")
("enb.mme_addr", bpo::value<string>(&args->stack.s1ap.mme_addr)->default_value("127.0.0.1"),"IP address of MME for S1 connection")
("enb.gtp_bind_addr", bpo::value<string>(&args->stack.s1ap.gtp_bind_addr)->default_value("192.168.3.1"), "Local IP address to bind for GTP connection")
("enb.s1c_bind_addr", bpo::value<string>(&args->stack.s1ap.s1c_bind_addr)->default_value("192.168.3.1"), "Local IP address to bind for S1AP connection")
("enb.n_prb", bpo::value<uint32_t>(&args->enb.n_prb)->default_value(25), "Number of PRB")
("enb.nof_ports", bpo::value<uint32_t>(&args->enb.nof_ports)->default_value(1), "Number of ports")
("enb.tm", bpo::value<uint32_t>(&args->enb.transmission_mode)->default_value(1), "Transmission mode (1-8)")
("enb.p_a", bpo::value<float>(&args->enb.p_a)->default_value(0.0f), "Power allocation rho_a (-6, -4.77, -3, -1.77, 0, 1, 2, 3)")
("enb.stack", bpo::value<string>(&args->stack.type)->default_value("lte"), "Type of the upper stack [lte, nr]")
("enb.enb_id", bpo::value<string>(&enb_id)->default_value("0x0"), "eNodeB ID")
("enb.name", bpo::value<string>(&args->stack.s1ap.enb_name)->default_value("srsenb01"), "eNodeB Name")
("enb.mcc", bpo::value<string>(&mcc)->default_value("001"), "Mobile Country Code")
("enb.mnc", bpo::value<string>(&mnc)->default_value("01"), "Mobile Network Code")
("enb.mme_addr", bpo::value<string>(&args->stack.s1ap.mme_addr)->default_value("127.0.0.1"),"IP address of MME for S1 connection")
("enb.gtp_bind_addr", bpo::value<string>(&args->stack.s1ap.gtp_bind_addr)->default_value("192.168.3.1"), "Local IP address to bind for GTP connection")
("enb.gtp_advertise_addr", bpo::value<string>(&args->stack.s1ap.gtp_advertise_addr)->default_value(""), "IP address of eNB to advertise for DL GTP-U Traffic")
("enb.s1c_bind_addr", bpo::value<string>(&args->stack.s1ap.s1c_bind_addr)->default_value("192.168.3.1"), "Local IP address to bind for S1AP connection")
("enb.n_prb", bpo::value<uint32_t>(&args->enb.n_prb)->default_value(25), "Number of PRB")
("enb.nof_ports", bpo::value<uint32_t>(&args->enb.nof_ports)->default_value(1), "Number of ports")
("enb.tm", bpo::value<uint32_t>(&args->enb.transmission_mode)->default_value(1), "Transmission mode (1-8)")
("enb.p_a", bpo::value<float>(&args->enb.p_a)->default_value(0.0f), "Power allocation rho_a (-6, -4.77, -3, -1.77, 0, 1, 2, 3)")
("enb_files.sib_config", bpo::value<string>(&args->enb_files.sib_config)->default_value("sib.conf"), "SIB configuration files")
("enb_files.rr_config", bpo::value<string>(&args->enb_files.rr_config)->default_value("rr.conf"), "RR configuration files")

12
srsenb/src/stack/upper/s1ap.cc
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@ -1176,7 +1176,11 @@ bool s1ap::send_ho_req_ack(const asn1::s1ap::ho_request_s& msg,
container.erab_admitted_list.value[i].load_info_obj(ASN1_S1AP_ID_ERAB_ADMITTED_ITEM);
auto& c = container.erab_admitted_list.value[i].value.erab_admitted_item();
c = admitted_bearers[i];
c.transport_layer_address = addr_to_asn1(args.gtp_bind_addr.c_str());
if (!args.gtp_advertise_addr.empty()) {
c.transport_layer_address = addr_to_asn1(args.gtp_advertise_addr.c_str());
} else {
c.transport_layer_address = addr_to_asn1(args.gtp_bind_addr.c_str());
}
// If E-RAB is proposed for forward tunneling
if (c.dl_g_tp_teid_present) {
@ -1669,7 +1673,11 @@ void s1ap::ue::get_erab_addr(uint16_t erab_id, transp_addr_t& transp_addr, asn1:
// Note: RRC does not yet update correctly gtpu transp_addr
transp_addr.resize(32);
uint8_t addr[4];
inet_pton(AF_INET, s1ap_ptr->args.gtp_bind_addr.c_str(), addr);
if (!s1ap_ptr->args.gtp_advertise_addr.empty()) {
inet_pton(AF_INET, s1ap_ptr->args.gtp_advertise_addr.c_str(), addr);
} else {
inet_pton(AF_INET, s1ap_ptr->args.gtp_bind_addr.c_str(), addr);
}
for (uint32_t j = 0; j < 4; ++j) {
transp_addr.data()[j] = addr[3 - j];
}

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