Re: [lwip-users] Help with PPP connection - modem disconnects for no obvious reason...

[Freddie Chopin]

On Wed, 2019-03-20 at 20:28 +0100, Sylvain Rochet wrote:
> Hi Freddie,
> 
> On Wed, Mar 20, 2019 at 07:37:27PM +0100, Freddie Chopin wrote:
> > On Wed, 2019-03-20 at 13:20 -0400, Patrick Klos wrote:
> > > For whatever reason, you're not responding to the CHAP
> > > challenges.
> > 
> > I assume this is because my user and password are just `""` (empty
> > strings), but this is just my very wild guess.
> 
> I don't think so, CHAP packets are huge and if PPP_USE_PBUF_RAM is
> not 
> set and your PBUF_POOL_BUFSIZE is a low value then packet allocation 
> will fail (lwIP PPP stack does not support chained pbuf), this is my 
> wild guess about what is happening.
> 
> Null secret is allowed in CHAP. See `secret_len = 0; /* assume null 
> secret if can't find one */` from chap-new.c.
> 
> Anyway, PAP does not need big packets, and you should try PAP 
> authentication with a null login and a null secret. Why compiling
> the 
> somewhat huge CHAP support when this is just fake authentication
> anyway ? :)

I've enabled PPP_USE_PBUF_RAM and here's the log:

-- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 --

ppp phase changed[1]: phase=0
ppp_connect[1]: holdoff=0
ppp phase changed[1]: phase=3
pppos_connect: unit 1: connecting
ppp_start[1]
ppp phase changed[1]: phase=6
pppos_send_config[1]: out_accm=FF FF FF FF
ppp_send_config[1]
pppos_recv_config[1]: in_accm=FF FF FF FF
ppp_recv_config[1]
ppp: auth protocols: PAP=1 CHAP=1 CHAP_MD5=1 CHAP_MS=1 CHAP_MS2=1 EAP=1
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x3123550b> <pcomp> <accomp>]
pppos_write[1]: len=24
ppp_start[1]: finished
pppos_input[1]: got 53 bytes
rcvd [LCP ConfReq id=0x0 <asyncmap 0x0> <auth chap MD5> <magic 0x50b674e9> 
<pcomp> <accomp>]
sent [LCP ConfAck id=0x0 <asyncmap 0x0> <auth chap MD5> <magic 0x50b674e9> 
<pcomp> <accomp>]
pppos_write[1]: len=29
pppos_input[1]: got 47 bytes
rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0x3123550b> <pcomp> <accomp>]
netif_set_mtu[1]: mtu=1500
pppos_send_config[1]: out_accm=0 0 0 0
ppp_send_config[1]
pppos_recv_config[1]: in_accm=0 0 0 0
ppp_recv_config[1]
ppp phase changed[1]: phase=7
pppos_input[1]: got 21 bytes
rcvd [LCP DiscReq id=0x1 magic=0x50b674e9]
pppos_input[1]: got 41 bytes
rcvd [CHAP Challenge id=0x1 <cefc86de84aa3f70aef9d363b441adf1>, name = 
"UMTS_CHAP_SRVR"]
No CHAP secret found for authenticating us to UMTS_CHAP_SRVR
sent [CHAP Response id=0x1 <18ccfbce71fa7190be42a696859524c4>, name = ""]
pppos_write[1]: len=25
pppos_input[1]: got 10 bytes
rcvd [CHAP Success id=0x1 ""]
CHAP authentication succeeded
CHAP authentication succeeded
ppp phase changed[1]: phase=9
ccp_set[1]: is_open=1, is_up=0, receive_method=0, transmit_method=0
sent [IPCP ConfReq id=0x1 <compress VJ 0f 01> <addr 0.0.0.0> <ms-dns1 0.0.0.0> 
<ms-dns2 0.0.0.0>]
pppos_write[1]: len=32
pppos_input[1]: got 14 bytes

-- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 --

Authentication succeeds, yet the modem still disconnects as previously
(; With PAP:

-- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 --

ppp phase changed[1]: phase=0
ppp_connect[1]: holdoff=0
ppp phase changed[1]: phase=3
pppos_connect: unit 1: connecting
ppp_start[1]
ppp phase changed[1]: phase=6
pppos_send_config[1]: out_accm=FF FF FF FF
ppp_send_config[1]
pppos_recv_config[1]: in_accm=FF FF FF FF
ppp_recv_config[1]
ppp: auth protocols: PAP=1 CHAP=0 CHAP_MD5=0 CHAP_MS=0 CHAP_MS2=0 EAP=0
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xd4163714> <pcomp> <accomp>]
pppos_write[1]: len=24
ppp_start[1]: finished
pppos_input[1]: got 55 bytes
rcvd [LCP ConfReq id=0x0 <asyncmap 0x0> <auth chap MD5> <magic 0x50b9186d> 
<pcomp> <accomp>]
sent [LCP ConfNak id=0x0 <auth pap>]
pppos_write[1]: len=12
pppos_input[1]: got 47 bytes
rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0xd4163714> <pcomp> <accomp>]
pppos_input[1]: got 53 bytes
rcvd [LCP ConfReq id=0x1 <asyncmap 0x0> <auth pap> <magic 0x50b9186d> <pcomp> 
<accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0x0> <auth pap> <magic 0x50b9186d> <pcomp> 
<accomp>]
pppos_write[1]: len=28
netif_set_mtu[1]: mtu=1500
pppos_send_config[1]: out_accm=0 0 0 0
ppp_send_config[1]
pppos_recv_config[1]: in_accm=0 0 0 0
ppp_recv_config[1]
ppp phase changed[1]: phase=7
sent [PAP AuthReq id=0x1 user="" password=""]
pppos_write[1]: len=10
pppos_input[1]: got 22 bytes
rcvd [LCP DiscReq id=0x2 magic=0x50b9186d]
pppos_input[1]: got 11 bytes
rcvd [PAP AuthAck id=0x1 ""]
PAP authentication succeeded
ppp phase changed[1]: phase=9
ccp_set[1]: is_open=1, is_up=0, receive_method=0, transmit_method=0
sent [IPCP ConfReq id=0x1 <compress VJ 0f 01> <addr 0.0.0.0> <ms-dns1 0.0.0.0> 
<ms-dns2 0.0.0.0>]
pppos_write[1]: len=32
pppos_input[1]: got 14 bytes

-- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 -- >8 --

With no authentication it's the same as previously.

I've also tried now with `AT+CGDATA="PPP",1`, but the result is
identical... );

Regards,
FCh