dhcpcd-discuss

Hi Hiroki

On 19/12/2019 06:13, Hiroki Takeuchi wrote:
> I am using a dhcpcd configuration which adds the destination as default route 
> (as suggested by the man page):
>
> interface ppp2
> metric 123
> static ip_address=
> destination routers
>
> It has been working fine with DHCPCD 6 until I upgraded to debian/ubuntu variant 
> of DHCP 7.1.0 and I tracked the error using gdb as it can be reproduced easily.
>
> #0  get_option (bootp=0x0, bootp_len=0, opt=opt@entry=26, opt_len=opt_len@entry=0x7ffd99ab97f0, ctx=<optimized out>, ctx=<optimized out>) at dhcp.c:174
> #1  0x0000563e96e22327 in get_option_uint16 (option=26 '\032', bootp_len=<optimized out>, bootp=<optimized out>, i=<synthetic pointer>, ctx=<optimized out>) at dhcp.c:314
> #2  dhcp_get_mtu (ifp=ifp@entry=0x563e97071220) at dhcp.c:698
> #3  0x0000563e96e28312 in inet_routerhostroute (routes=0x7ffd99ab9990, ifp=0x563e97071220) at ipv4.c:417
> #4  inet_getroutes (ctx=ctx@entry=0x7ffd99abaaa0, routes=routes@entry=0x7ffd99ab9990) at ipv4.c:438
> #5  0x0000563e96e194b3 in rt_build (ctx=0x7ffd99abaaa0, af=af@entry=2) at route.c:515
> #6  0x0000563e96e28d4b in ipv4_applyaddr (arg=arg@entry=0x563e970791b0) at ipv4.c:761
> #7  0x0000563e96e234f8 in dhcp_bind (ifp=ifp@entry=0x563e970791b0) at dhcp.c:2335
> #8  0x0000563e96e2381b in dhcp_arp_bind (ifp=0x563e970791b0) at dhcp.c:2446
> #9  dhcp_static (ifp=ifp@entry=0x563e97069e80) at dhcp.c:2476
> #10 0x0000563e96e27018 in dhcp_start1 (arg=0x563e97069e80, arg@entry=0x563e970791b0) at dhcp.c:3692
> #11 0x0000563e96e279e0 in dhcp_start (ifp=0x563e970791b0) at dhcp.c:3866
> #12 0x0000563e96e0e55c in dhcpcd_startinterface (arg=0x563e970791b0) at dhcpcd.c:921
> #13 0x0000563e96e0e881 in reconf_reboot (action=1, argc=3, argv=0x7ffd99ab9da0, oi=2, ctx=<optimized out>) at dhcpcd.c:1219
> #14 0x0000563e96e0f7de in dhcpcd_handleargs (ctx=0x7ffd99abaaa0, fd=fd@entry=0x563e9704f470, argc=argc@entry=3, argv=argv@entry=0x7ffd99ab9da0) at dhcpcd.c:1477
> #15 0x0000563e96e0c5ba in control_handle_data (arg=0x563e9704f470) at control.c:143
> #16 0x0000563e96e10aab in eloop_start (eloop=0x563e97063630, signals=0x7ffd99ababa8) at eloop.c:978
> #17 0x0000563e96e0b36b in main (argc=<optimized out>, argv=<optimized out>) at dhcpcd.c:2024
>
> And from my syslog I also noticed a weird log message indicating requirement of 
> host route in another interface with the PPP interface destination IP.
> dhcpcd[13415]: control command: dhcpcd -n ppp2
> dhcpcd[13415]: ppp2: carrier acquired
> dhcpcd[13415]: ppp2: IAID 70:70:70:32
> dhcpcd[13415]: ppp2: using static address 10.10.10.170/32 <http://10.10.10.170/32>
> dhcpcd[13415]: eno3: router 10.10.10.1 requires a host route
> systemd[1]: dhcpcd.service: Main process exited, code=killed, status=11/SEGV
> The PPP interface:
> 23: ppp2: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1492 qdisc fq_codel 
> state UNKNOWN group WAN qlen 3
>      link/ppp
>      inet 10.10.10.170 peer 10.10.10.1/32 <http://10.10.10.1/32> scope global ppp2
>         valid_lft forever preferred_lft forever
>
> After comparing dhcpcd 6 and dhcpcd 7, and found out that the "routers" 
> looked-up in  inet_routerhostroute are from multiple interfaces, as opposed to 
> dhcpcd 6 add_router_host_route is only adding the routes from a single 
> interface. Hence, I attempted to patch inet_getroutes which apparently solved 
> this issue.
>
> This is the first time I attempted to modify dhcpcd, sorry if the patch doesn't 
> match the coding guidelines or principles. Do let me know what you guys think 
> about this issue and whether there's a better solution to this issue. Thanks!

Thanks for the patch! It doesn't solve the actual problem your backtrace shows 
though - frame #0 shows that the bootp argument is NULL.

I've pushed a different patch here which should solve it:
https://roy.marples.name/cgit/dhcpcd.git/commit/?h=dhcpcd-7&id=75f2832a88b8f5a3078179404b149b7cd9623dbf

Let me know how it works for you.

Roy