MPD: FreeBSD PPP daemon / Discussion / Help: Problems with Sierra Wireless EM7421

Hi,

I have a FreeBSD 13.3 machine with Sierra Wireless EM7421 LTE/4G modem. I have been trying to get mpd5 (mpd5-5.9_18) working with without much success. The configuration I'm using is the same which works with older devices having SimTech modems.

My configuration looks like this:

mobile:
        create bundle static mobile
        set bundle links B-Link
        set bundle enable ipcp
        set bundle enable compression
        set iface route default
        set ipcp ranges 0.0.0.0/0 10.0.0.1/0
        set ipcp enable req-pri-dns
        set ipcp enable req-sec-dns
        set iface enable nat
        set iface up-script /usr/local/etc/mpd5/up.script
        set iface down-script /usr/local/etc/mpd5/down.script
        log +chat +link2 +phys2 +lcp255 +ipcp2 +frame +fsm2 +bund2 +ccp2 +chat2
        create link static B-Link modem
        set link action bundle mobile
        set modem device /dev/cuaU0.2
        set modem speed 921600
        set modem script dial-mobile
        set modem watch -cd
        set modem watch -dsr
        set auth authname dummy
        set auth password dummy
        set link keep-alive 6 60
        set link max-redial 0
        open

When started, everything seems to come up but immediately after that I see this in log:

mpd[3393]: [B-Link] LCP: rec'd Terminate Request #66 (Opened)
mpd[3393]: [B-Link] LCP: state change Opened --> Stopping

and the connection closes. I'll attach the complete logfile.

The modem itself seems to work, because when I try to use it with user-level ppp in FreeBSD, connection comes up and stays up. However, I would prefer to use mpd, but don't understand what is wrong with my configuration.

If I disable ipcp then lcp stays up, but the connection is obviously quite useless then.

mpd.log

Eugene Grosbein - 2024-09-14

First, disable IPCP vjcomp option as remote side rejects it anyway:

set ipcp disable vjcomp

And retry. If it does not help, please collect similar log of user-level ppp that includes IPCP negotiation to compare, and post it.

If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

Eugene Grosbein - 2024-09-14

Also, remote side rejects CCP protocol, so change "set bundle enable compression" to "set bundle disable compression"

If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

Ari Suutari - 2024-09-16

Disabling vjcomp and CCP didn't help. Here is mpd2.log from connection attempt with those disabled. I'll attach also ppp.log from user-level ppp which contains successful negotiation.

mpd2.log

ppp.log

If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
- Eugene Grosbein - 2024-09-16
  
  The only notable difference left is accmap option, try to add this:
  set link accmap 0
  
  If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
  - Ari Suutari - 2024-09-16
    
    Unfortunately, with this change, it still behaves same as before.
    
    If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
    - Eugene Grosbein - 2024-09-16
      
      Anyway, please post latest mpd log.
      
      If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

Ari Suutari - 2024-09-16

Here is the latest log.

mpd3.log

If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
- Eugene Grosbein - 2024-09-16
  
  The log shows the following:
  
  Sep 16 12:08:38 box-174 mpd[6329]: [B-Link] LCP: SendIdent #1 Sep 16 12:08:38 box-174 mpd[6329]: [B-Link] MESG: synciot Sep 16 12:08:38 box-174 mpd[6329]: [B-Link] xmit frame to link proto=0xc021 Sep 16 12:08:38 box-174 mpd[6329]: ff 03 c0 21 0c 01 00 10 21 10 f1 31 73 79 6e 63 ...!....!..1sync Sep 16 12:08:38 box-174 mpd[6329]: 69 6f 74 00
  
  The documentation https://mpd.sourceforge.net/doc5/mpd20.html#20 tells:
  
  set link ident string This enables the sending of an identification string to the peer via the LCP Ident code. The Ident string is sent when the link is brought up. This is useful for debugging, etc. and is meant to be human-readable. However, it confuses some broken PPP implementations. Setting an empty string disables this feature; this is the default.
  
  Your configuration above does not include "set link ident" but you seem to have it really. Comment it out and retry.
  
  Last edit: Eugene Grosbein 2024-09-16
  
  If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
  - Ari Suutari - 2024-09-16
    
    Oh yes, I tried to add it because there was something similar in ppp.log. Removed now, fresh log and config attached.
    
    mpd.conf
    
    mpd4.log
    
    If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
    - Eugene Grosbein - 2024-09-16
      
      OTOH, maybe other side wants to serve only "known" PPP clients. Try to pretend this is user-ppp:
      
      set link ident "user-ppp 3.4.2"
      
      Last edit: Eugene Grosbein 2024-09-16
      
      If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
      - Ari Suutari - 2024-09-16
        
        Tried that. Unfortunately no luck.
        
        If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
        
        Eugene Grosbein - 2024-09-16
        
        Perhaps, your ISP somehow detects you are "sharing" the connection among multiple devices while it does not permit that? Try filtering all IP traffic running over ng0 interface for some time to see if termination delays, too?
        
        If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
        
        Ari Suutari - 2024-09-17
        
        It's not ISP I'm talking to. It's LTE/4G modem, which uses PPP between it and host system. This is very common with such devices, but there is now PPP going out from modem's radio!
        
        https://source.sierrawireless.com/resources/airprime/minicard/75xx/41111748-airprime-em75xx-at-command-reference/
        
        Section 13 in manual "GSM/WCDMA AT COMMANDS", page 131.
        
        As these modems can achive quite high network speeds, we have been preferring mpd5 instead FreeBSD's user mode ppp (which pushes all the traffic thru user mode process).
        
        If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
        
        Eugene Grosbein - 2024-09-17
        
        Make sure that your AT-commands script for the modem initializes it exactly same way as one for user-ppp.
        
        If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
        
        Ari Suutari - 2024-09-17
        
        There is only one relevant initialization setting in mpd.script (AT+CGDCONT), which is same for both.
        
        If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

Ari Suutari - 2024-09-17

Is it possible to have mpd5 log serial line data ? Something like this in user-mode ppp:

Sep 17 10:00:59 synciot-174 ppp[28658]: tun1: Debug: proto_LayerPush: Using 0xc021 Sep 17 10:00:59 synciot-174 ppp[28658]: tun1: HDLC: hdlc_Output Sep 17 10:00:59 synciot-174 ppp[28658]: tun1: HDLC: ff 03 c0 21 01 01 00 18 08 02 07 02 02 06 00 00 ...!............ Sep 17 10:00:59 synciot-174 ppp[28658]: tun1: HDLC: 00 00 01 04 05 dc 05 06 8f d7 8c 75 33 58 ...........u3X
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
- Eugene Grosbein - 2024-09-17
  
  Your logs already have it, for example:
  
  Sep 16 12:08:38 box-174 mpd[6329]: [B-Link] rec'd 27 bytes frame from link proto=0xc021 Sep 16 12:08:38 box-174 mpd[6329]: c0 21 01 06 00 19 02 06 00 00 00 00 03 05 c2 23 .!.............# Sep 16 12:08:38 box-174 mpd[6329]: 05 05 06 3a 14 eb db 07 02 08 02 ...:.......
  
  If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
- Eugene Grosbein - 2024-09-17
  
  You could find useful ktrace(1) kernel facility to record system calls and sent/received data of mpd5 process:
  
  ktrace -i mpd5 ... kdump
  
  If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

Ari Suutari - 2024-09-18

I'm starting to suspect that problem is not in mpd5, but in ng_ kernel modules that are being used here. If I disable ipcp the link stays up. And ipcp happens in ng_ module (as far as I understand).

If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

Ari Suutari - 2024-09-18

Upgraded to FreeBSD 14.1 and now it works.

If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

Problems with Sierra Wireless EM7421

FreeBSD Multi PPP daemon

Forums

Help

Problems with Sierra Wireless EM7421

Problems with Sierra Wireless EM7421

FreeBSD Multi PPP daemon

Forums

Help

Problems with Sierra Wireless EM7421 document.SUBSCRIPTION_OPTIONS = { "thing": "topic", "subscribed": false, "url": "subscribe", "icon": { "css": "fa fa-envelope-o" } };

Problems with Sierra Wireless EM7421