Re: PPP Modem Hangup

On analyzing the logs further, I noticed that I can ping only from
AOSP target device to Ubuntu Machine and not the other way around.

On Fri, Sep 13, 2024 at 11:33 AM Devesh Chipade <[email protected]> wrote:
>
> 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*
> >
> >
> >