UE（phone）cannot connect to the Internet after using srsepc_if_masq.sh

[chaosyizer]

Issue Description

[Describe the issue in detail]
Firstly, I successfully deployed srsepc and srsenb on the same computer. After running srsepc_if_masq.sh, the phone was able to connect to the internet with no issues.
However, after deploying srsepc and srsenb on two different computers, and modifying the epc.conf on PC1 and the enb.conf on PC2, the epc and enb were able to connect to each other. The phone was also able to connect to this network, but the only issue was that the phone could not access the internet.

Setup Details

[Specify details of the test setup. This would help us reproduce the problem reliably]
e.g. Network configuration, Operation System, Hardware, RF front-end, library and driver versions
PC1:UBUNTU22.04LTS PC2:UBUNTU22.04LTS
SDR: USRP B210
UE(PHONE):HONOR V30

srsran 4g version
sdrpw123@sdrpw123-B460MAORUSELITE:/srsRAN_4G$ git branch --show-current
master
sdrpw123@sdrpw123-B460MAORUSELITE:/srsRAN_4G$ git rev-parse HEAD
ec29b0c

Expected Behavior

[What you expect to happen]
srsepc and srsenb are deployed on two separate computers. After using srsepc_if_masq.sh, the phone can access the internet.

Actual Behaviour

[What happens instead e.g. error message]
When srsepc and srsenb are deployed on the same computer, the phone can access the internet without any issues. However, when srsepc and srsenb are deployed on separate computers, there is only one difference: the phone is unable to access the internet.

Steps to reproduce the problem

[Tell us how to reproduce this issue e.g. RF setup, application config files]
enb.conf on PC2:

epc.conf on PC1:

The output of srsepc during runtime：
Built in Release mode using commit ec29b0c on branch master.

--- Software Radio Systems EPC ---

Couldn't open , trying /root/.config/srsran/epc.conf
Reading configuration file /root/.config/srsran/epc.conf...
Couldn't open user_db.csv, trying /root/.config/srsran/user_db.csv
HSS Initialized.
MME S11 Initialized
MME GTP-C Initialized
MME Initialized. MCC: 0xf901, MNC: 0xff70
SPGW GTP-U Initialized.
SPGW S11 Initialized.
SP-GW Initialized.
Received S1 Setup Request.
S1 Setup Request - eNB Name: srsenb01, eNB id: 0x19b
S1 Setup Request - MCC:901, MNC:70
S1 Setup Request - TAC 7, B-PLMN 0x9f107
S1 Setup Request - Paging DRX v128
Sending S1 Setup Response

The output of srsepc during runtime：
Active RF plugins: libsrsran_rf_uhd.so
Inactive RF plugins:
--- Software Radio Systems LTE eNodeB ---

Couldn't open , trying /root/.config/srsran/enb.conf
Reading configuration file /root/.config/srsran/enb.conf...
Couldn't open sib.conf, trying /root/.config/srsran/sib.conf
Couldn't open rr.conf, trying /root/.config/srsran/rr.conf
Couldn't open rb.conf, trying /root/.config/srsran/rb.conf
WARNING: cpu0 scaling governor is not set to performance mode. Realtime processing could be compromised. Consider setting it to performance mode before running the application.

Built in Release mode using commit ec29b0c on branch master.

Opening 1 channels in RF device=default with args=default
Supported RF device list: UHD file
Trying to open RF device 'UHD'
[INFO] [UHD] linux; GNU C++ version 11.2.0; Boost_107400; UHD_4.1.0.5-3
[INFO] [LOGGING] Fastpath logging disabled at runtime.
Opening USRP channels=1, args: type=b200,master_clock_rate=23.04e6
[INFO] [UHD RF] RF UHD Generic instance constructed
[INFO] [B200] Detected Device: B210
[INFO] [B200] Operating over USB 3.
[INFO] [B200] Initialize CODEC control...
[INFO] [B200] Initialize Radio control...
[INFO] [B200] Performing register loopback test...
[INFO] [B200] Register loopback test passed
[INFO] [B200] Performing register loopback test...
[INFO] [B200] Register loopback test passed
[INFO] [B200] Asking for clock rate 23.040000 MHz...
[INFO] [B200] Actually got clock rate 23.040000 MHz.
RF device 'UHD' successfully opened

==== eNodeB started ===
Type to view trace
Setting frequency: DL=2680.0 Mhz, UL=2560.0 MHz for cc_idx=0 nof_prb=50

after ue connect:
srsepc:
Received S1 Setup Request.
S1 Setup Request - eNB Name: srsenb01, eNB id: 0x19b
S1 Setup Request - MCC:901, MNC:70
S1 Setup Request - TAC 7, B-PLMN 0x9f107
S1 Setup Request - Paging DRX v128
Sending S1 Setup Response
Initial UE message: LIBLTE_MME_MSG_TYPE_ATTACH_REQUEST
Received Initial UE message -- Attach Request
Attach request -- M-TMSI: 0xe1b22e4d
Attach request -- eNB-UE S1AP Id: 1
Attach request -- Attach type: 2
Attach Request -- UE Network Capabilities EEA: 11110000
Attach Request -- UE Network Capabilities EIA: 01110000
Attach Request -- MS Network Capabilities Present: false
PDN Connectivity Request -- EPS Bearer Identity requested: 0
PDN Connectivity Request -- Procedure Transaction Id: 7
PDN Connectivity Request -- ESM Information Transfer requested: true
UL NAS: Received Identity Response
ID Response -- IMSI: 901700000020936
Downlink NAS: Sent Authentication Request
UL NAS: Received Authentication Response
Authentication Response -- IMSI 901700000020936
UE Authentication Accepted.
Generating KeNB with UL NAS COUNT: 0
Downlink NAS: Sending NAS Security Mode Command.
UL NAS: Received Security Mode Complete
Security Mode Command Complete -- IMSI: 901700000020936
Sending ESM information request
UL NAS: Received ESM Information Response
ESM Info: APN ims
Getting subscription information -- QCI 9
Sending Create Session Request.
Creating Session Response -- IMSI: 901700000020936
Creating Session Response -- MME control TEID: 1
Received GTP-C PDU. Message type: GTPC_MSG_TYPE_CREATE_SESSION_REQUEST
SPGW: Allocated Ctrl TEID 1
SPGW: Allocated User TEID 1
SPGW: Allocate UE IP 172.16.0.2
Received Create Session Response
Create Session Response -- SPGW control TEID 1
Create Session Response -- SPGW S1-U Address: 127.0.1.100
SPGW Allocated IP 172.16.0.2 to IMSI 901700000020936
Adding attach accept to Initial Context Setup Request
Sent Initial Context Setup Request. E-RAB id 5
Received Initial Context Setup Response
E-RAB Context Setup. E-RAB id 5
E-RAB Context -- eNB TEID 0x1; eNB GTP-U Address 192.168.5.3
UL NAS: Received Attach Complete
Unpacked Attached Complete Message. IMSI 901700000020936
Unpacked Activate Default EPS Bearer message. EPS Bearer id 5
Received GTP-C PDU. Message type: GTPC_MSG_TYPE_MODIFY_BEARER_REQUEST
Sending EMM Information

srsenb:
==== eNodeB started ===
Type to view trace
Setting frequency: DL=2680.0 Mhz, UL=2560.0 MHz for cc_idx=0 nof_prb=50
RACH: tti=6741, cc=0, pci=1, preamble=32, offset=1, temp_crnti=0x46
User 0x46 connected

Additional Information

[Any additional information, configuration or data that might be necessary to reproduce the issue]
Despite the following issues being reported, in fact, when srsepc and srsenb are deployed on the same computer, this problem was encountered as well, but everything was running normally.

Couldn't open , trying /root/.config/srsran/epc.conf
Reading configuration file /root/.config/srsran/epc.conf...
Couldn't open user_db.csv, trying /root/.config/srsran/user_db.csv

So, I speculate that these three lines of error messages can be temporarily ignored for now.

If you need any additional information, please point it out in the comments section, thank you!