Re: PPP Modem Hangup

Posting more details:

On Ubuntu:

$ ip route show
default via 192.168.0.1 dev wlp5s0 proto dhcp src 192.168.0.79 metric 600
10.0.0.0/24 dev ppp0 scope link
10.0.0.2 dev ppp0 proto kernel scope link src 10.0.0.1
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown
192.168.0.0/24 dev wlp5s0 proto kernel scope link src 192.168.0.79 metr

$ ip addr show
59: ppp0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc
pfifo_fast state UNKNOWN group default qlen 3
    link/ppp
    inet 10.0.0.1 peer 10.0.0.2/32 scope global ppp0
       valid_lft forever preferred_lft forever

~$ sudo tcpdump -i ppp0
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on ppp0, link-type LINUX_SLL (Linux cooked v1), snapshot
length 262144 bytes
11:29:02.068203 IP Devesh > 10.0.0.2: ICMP echo request, id 56351, seq
5744, length 64
11:29:02.394650 IP 10.0.0.2 > Devesh: ICMP echo request, id 32, seq
5882, length 64
11:29:02.394673 IP Devesh > 10.0.0.2: ICMP echo reply, id 32, seq
5882, length 64
11:29:02.490505 IP 10.0.0.2 > Devesh: ICMP echo request, id 28, seq
428, length 64
11:29:02.490533 IP Devesh > 10.0.0.2: ICMP echo reply, id 28, seq 428, length 64
11:29:02.570513 IP 10.0.0.2 > Devesh: ICMP echo request, id 29, seq
239, length 64
11:29:02.570533 IP Devesh > 10.0.0.2: ICMP echo reply, id 29, seq 239, length 64
11:29:03.092195 IP Devesh > 10.0.0.2: ICMP echo request, id 56351, seq
5745, length 64
11:29:03.386211 IP 10.0.0.2 > Devesh: ICMP echo request, id 32, seq
5883, length 64
11:29:03.386238 IP Devesh > 10.0.0.2: ICMP echo reply, id 32, seq
5883, length 64
11:29:03.482223 IP 10.0.0.2 > Devesh: ICMP echo request, id 28, seq
429, length 64
11:29:03.482246 IP Devesh > 10.0.0.2: ICMP echo reply, id 28, seq 429, length 64
11:29:03.578234 IP 10.0.0.2 > Devesh: ICMP echo request, id 29, seq
240, length 64
11:29:03.578258 IP Devesh > 10.0.0.2: ICMP echo reply, id 29, seq 240, length 64
11:29:04.116196 IP Devesh > 10.0.0.2: ICMP echo request, id 56351, seq
5746, length 64
11:29:04.393801 IP 10.0.0.2 > Devesh: ICMP echo request, id 32, seq
5884, length 64
11:29:04.393826 IP Devesh > 10.0.0.2: ICMP echo reply, id 32, seq
5884, length 64


On Android Target Device:

# ip route
default dev ppp0 scope link
10.0.0.0/24 dev ppp0 scope link
10.0.0.1 dev ppp0 proto kernel scope link src 10.0.0.2

# ip addr show
72: ppp0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc
pfifo_fast state UNKNOWN group default qlen 3
    link/ppp
    inet 10.0.0.2 peer 10.0.0.1/32 scope global ppp0
       valid_lft forever preferred_lft forever

# ifconfig
ppp0      Link encap:Point-to-Point Protocol
          inet addr:10.0.0.2  P-t-P:10.0.0.1  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:204583 errors:0 dropped:0 overruns:0 frame:0
          TX packets:137381 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3
          RX bytes:17453623 TX bytes:11539856

# tcpdump -i ppp0
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on ppp0, link-type LINUX_SLL (Linux cooked v1), snapshot
length 262144 bytes
11:27:47.371173 IP 10.0.0.1 > 10.0.0.2: ICMP echo reply, id 32, seq
5969, length 64
11:27:47.865949 IP 10.0.0.1 > 10.0.0.2: ICMP echo request, id 56351,
seq 5830, length 64
11:27:47.979345 IP 10.0.0.2 > 10.0.0.1: ICMP echo request, id 29, seq
327, length 64
11:27:47.979903 IP 10.0.0.2 > 10.0.0.1: ICMP echo request, id 32, seq
5970, length 64
11:27:47.980717 IP 10.0.0.2 > 10.0.0.1: ICMP echo request, id 28, seq
516, length 64
11:27:48.182932 IP 10.0.0.1 > 10.0.0.2: ICMP echo reply, id 29, seq
327, length 64
11:27:48.275624 IP 10.0.0.1 > 10.0.0.2: ICMP echo reply, id 32, seq
5970, length 64
11:27:48.363885 IP 10.0.0.1 > 10.0.0.2: ICMP echo reply, id 28, seq
516, length 64
11:27:48.891693 IP 10.0.0.1 > 10.0.0.2: ICMP echo request, id 56351,
seq 5831, length 64
11:27:48.979785 IP 10.0.0.2 > 10.0.0.1: ICMP echo request, id 29, seq
328, length 64
11:27:48.981057 IP 10.0.0.2 > 10.0.0.1: ICMP echo request, id 32, seq
5971, length 64
11:27:48.981469 IP 10.0.0.2 > 10.0.0.1: ICMP echo request, id 28, seq
517, length 64
11:27:49.190116 IP 10.0.0.1 > 10.0.0.2: ICMP echo reply, id 29, seq
328, length 64
11:27:49.281473 IP 10.0.0.1 > 10.0.0.2: ICMP echo reply, id 32, seq
5971, length 64
11:27:49.368639 IP 10.0.0.1 > 10.0.0.2: ICMP echo reply, id 28, seq
517, length 64
11:27:49.913433 IP 10.0.0.1 > 10.0.0.2: ICMP echo request, id 56351,
seq 5832, length 64
11:27:49.980826 IP 10.0.0.2 > 10.0.0.1: ICMP echo request, id 32, seq
5972, length 64
11:27:49.981377 IP 10.0.0.2 > 10.0.0.1: ICMP echo request, id 29, seq
329, length 64
11:27:49.982190 IP 10.0.0.2 > 10.0.0.1: ICMP echo request, id 28, seq
518, length 64
11:27:50.193380 IP 10.0.0.1 > 10.0.0.2: ICMP echo reply, id 32, seq
5972, length 64

On Fri, Sep 13, 2024 at 11:00 AM Michael Richardson <[email protected]> wrote:
>
>
> Devesh Chipade <[email protected]> wrote:
>     > I am still not able to ping into ubuntu/linux or into my aosp target
>     > device without explicitly mentioning -I ppp0 interface.  ping -I ppp0
>     > 10.0.0.1 / ping -I ppp0 10.0.0.2 works but ping 10.0.0.1 / ping
>     > 10.0.0.2 does not work,
>
> Android does stuff with the networking stack so that it can live in multiple
> provider domains.   So the default route (if it exists) often lives in a
> alternate routing table.
>
>     > I have verified the ip route, ip tables, ip addr show as well as
>     > ifconfig (both on linux and aosp target). Seems to be all good in it.
>     > Any suggestions?
>
> you didn't post details, but..
>
> if you tcpdump on your Ubuntu side, you'll probably see that AOSP side has
> picked some other IP address as the source.  If you really want to fix that,
> then add a route back to the ppp0 device on the ubuntu side, but probably you
> just need to make sure that the Android side always uses the right source IP.
>
>
>
>
> --
> Michael Richardson <[email protected]>, Sandelman Software Works
>  -= IPv6 IoT consulting =-                      *I*LIKE*TRAINS*
>
>
>