gdb -ex=run  --args accel-pppd -c /etc/accel-ppp.conf -p /var/run/accel-ppp.pid
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-110.el7
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/local/sbin/accel-pppd...done.
Starting program: /usr/local/sbin/accel-pppd -c /etc/accel-ppp.conf -p /var/run/accel-ppp.pid
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
[New Thread 0x7ffff4886700 (LWP 91653)]
[New Thread 0x7ffff4085700 (LWP 91654)]
[New Thread 0x7ffff7fc6700 (LWP 91657)]
[New Thread 0x7ffff3884700 (LWP 91658)]
[New Thread 0x7ffff3783700 (LWP 91659)]
[New Thread 0x7ffff3682700 (LWP 91660)]
[New Thread 0x7ffff3581700 (LWP 91661)]
[New Thread 0x7ffff3480700 (LWP 91662)]
[New Thread 0x7ffff337f700 (LWP 91663)]
[New Thread 0x7ffff327e700 (LWP 91664)]
[New Thread 0x7ffff317d700 (LWP 91665)]
[New Thread 0x7ffff307c700 (LWP 91666)]
[New Thread 0x7ffff2f7b700 (LWP 91667)]
[New Thread 0x7ffff2e7a700 (LWP 91668)]
[New Thread 0x7ffff2d79700 (LWP 91669)]
[New Thread 0x7ffff2c78700 (LWP 91670)]
[New Thread 0x7ffff2b77700 (LWP 91671)]
[New Thread 0x7ffff2a76700 (LWP 91672)]
[New Thread 0x7ffff2975700 (LWP 91673)]
[New Thread 0x7ffff2174700 (LWP 91674)]
​
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff2b77700 (LWP 91671)]
0x00007ffff69429e7 in __strcat_sse2_unaligned () from /lib64/libc.so.6
Missing separate debuginfos, use: debuginfo-install glibc-2.17-307.el7.1.x86_64 keyutils-libs-1.5.8-3.el7.x86_64 krb5-libs-1.15.1-19.el7.x86_64 libcom_err-1.42.9-12.el7_5.x86_64 libselinux-2.5-12.el7.x86_64 openssl-libs-1.0.2k-12.el7.x86_64 pcre-8.32-17.el7.x86_64 zlib-1.2.7-17.el7.x86_64
(gdb) bt
#0  0x00007ffff69429e7 in __strcat_sse2_unaligned () from /lib64/libc.so.6
#1  0x00007ffff52cd49f in ev_ses_authorized1 (ses=0x7fffec001c70) at /opt/accel-ppp-code_sf/accel-pppd/logs/log_file.c:465
#2  0x00007ffff7bd7952 in triton_event_fire (ev_id=5, arg=0x7fffec001c70) at /opt/accel-ppp-code_sf/accel-pppd/triton/event.c:103
#3  0x00007ffff50b5feb in auth_result (ses=0x7fffec001b88, r=0) at /opt/accel-ppp-code_sf/accel-pppd/ctrl/ipoe/ipoe.c:647
#4  0x00007ffff50b64c2 in ipoe_session_start (ses=0x7fffec001b88) at /opt/accel-ppp-code_sf/accel-pppd/ctrl/ipoe/ipoe.c:745
#5  0x00007ffff7bd46ee in ctx_thread (ctx=0x7fffec001f08) at /opt/accel-ppp-code_sf/accel-pppd/triton/triton.c:272
#6  0x00007ffff7bd43eb in triton_thread (thread=0x12b7a80) at /opt/accel-ppp-code_sf/accel-pppd/triton/triton.c:192
#7  0x00007ffff77b3ea5 in start_thread () from /lib64/libpthread.so.0
#8  0x00007ffff69a38dd in clone () from /lib64/libc.so.6
(gdb) bt full
#0  0x00007ffff69429e7 in __strcat_sse2_unaligned () from /lib64/libc.so.6
No symbol table info available.
#1  0x00007ffff52cd49f in ev_ses_authorized1 (ses=0x7fffec001c70) at /opt/accel-ppp-code_sf/accel-pppd/logs/log_file.c:465
        lpd = 0x7fffe40019d8
        fname = 0x7fffe4001f30 "/var/log/accel-ppp/per-user//"
#2  0x00007ffff7bd7952 in triton_event_fire (ev_id=5, arg=0x7fffec001c70) at /opt/accel-ppp-code_sf/accel-pppd/triton/event.c:103
        ev = 0x68b640
        h = 0x68efc0
#3  0x00007ffff50b5feb in auth_result (ses=0x7fffec001b88, r=0) at /opt/accel-ppp-code_sf/accel-pppd/ctrl/ipoe/ipoe.c:647
        username = 0x0
#4  0x00007ffff50b64c2 in ipoe_session_start (ses=0x7fffec001b88) at /opt/accel-ppp-code_sf/accel-pppd/ctrl/ipoe/ipoe.c:745
        r = 0
        passwd = 0x7fffec001f78 "x\037"
        username = 0x7fffe40019a0 "p1p2.777"
        pass = 0x7ffff7bd3cea <list_del+38> "H\213E\370", <incomplete sequence \307>
        __PRETTY_FUNCTION__ = "ipoe_session_start"
#5  0x00007ffff7bd46ee in ctx_thread (ctx=0x7fffec001f08) at /opt/accel-ppp-code_sf/accel-pppd/triton/triton.c:272
        h = 0x7ffff7dda330 <sleep_threads>
        t = 0x7ffff50b4eae <ipoe_ctx_switch>
        call = 0x12b4be8
        tt = 140737152818072
        events = 32767
#6  0x00007ffff7bd43eb in triton_thread (thread=0x12b7a80) at /opt/accel-ppp-code_sf/accel-pppd/triton/triton.c:192
        set = {__val = {516, 0 <repeats 15 times>}}
        sig = 10
        need_free = 0
        stack = 0x0
#7  0x00007ffff77b3ea5 in start_thread () from /lib64/libpthread.so.0
No symbol table info available.
#8  0x00007ffff69a38dd in clone () from /lib64/libc.so.6
No symbol table info available.

[ipoe]
gw-ip-address=100.64.0.1/24
ip-pool=ipoe2
interface=re:^p1p2\.777$,mode=L2,shared=1,ifcfg=1,start=dhcpv4,ip-unnumbered=1

[ip-pool]
gw-ip-address=100.64.0.1/24
100.64.0.2/24,name=ipoe2

В логах успешная авторизация и (null) 

[2020-09-02 19:32:21.474] accel-ppp version 1.12.0-72-ged7b287
[2020-09-02 19:32:21.474] open ns (null)
[2020-09-02 19:32:21.489] ipoe: start interface p1p2.777 (mode=L2,shared=1,ifcfg=1,start=dhcpv4,ip-unnumbered=1)
[2020-09-02 19:32:23.175] p1p2.777: : recv [DHCPv4 Discover xid=364e8649 chaddr=b4:b6:87:93:8b:1d <Message-Type Discover> <Client-ID 01b4b686958a1e> <Host-Name tests> <Vendor-Class 4d53465420352e30> <Request-List Subnet,Domain-Name,Router,DNS,44,46,47,31,Route,Classless-Route,249,Vendor-Specific>]
[2020-09-02 19:32:23.175] ipoe0: e9df193b22bbbd7b: create interface ipoe0 parent p1p2.777
[2020-09-02 19:32:23.175] ipoe0: e9df193b22bbbd7b: (null): authentication succeeded