Segfault with ifname filter and RTD_UNREACHABLE

[Lars Gierth]

Hi all,

I'm migrating a bigger Babel network from Bird 2.17.x to 3.1.x. This is 
on OpenWrt snapshot x86_64 with latest Bird stable-v3.1 branch. Shortly 
after starting Bird, it segfaults.

I tested all the individual filter statements in my config and confirmed 
it's those comparing against ifname, e.g.:

     if ifname = "ts_wg0" then

It doesn't segfault if I first check for unreachable:

     if dest != RTD_UNREACHABLE && ifname = "ts_wg0" then

The docs state that ifname returns an empty string for sink routes, and 
that's what worked for us in 2.17.x, but maybe that broke somehow? 
Anyway, with this workaround I can continue testing and rolling out.

Here's the backtrace. The config is attached and binary+coredump can be 
downloaded here: 
https://github.com/user-attachments/files/23552707/bird-coredump.zip Let 
me know if the coredump is broken, gdb did say "memory read failed".

     #0  0x00007ffff7fabd80 in ?? ()
     #1  0x000000000041f881 in val_same (v1=v1 at entry=0x7fffffffdb90, 
v2=0x7fffffffdba8) at filter/data.c:281
     #2  0x0000000000415bd7 in interpret (line=<optimized out>, 
argc=argc at entry=0, argv=argv at entry=0x0, resc=resc at entry=0, 
resv=resv at entry=0x0, fs=<optimized out>) at filter/f-inst.c:453
     #3  0x000000000041efb6 in f_run_args (filter=0x7ffff7f31300, 
rte=rte at entry=0x7fffffffe8c0, argc=argc at entry=0, argv=argv at entry=0x0, 
flags=flags at entry=0) at filter/filter.c:232
     #4  0x000000000041f01b in f_run (filter=<optimized out>, 
rte=rte at entry=0x7fffffffe8c0, flags=flags at entry=0) at filter/filter.c:215
     #5  0x000000000045c328 in channel_rte_import 
(c=c at entry=0x7ffff7e61830, n=n at entry=0x7ffff7df6ea8, 
new=new at entry=0x7fffffffe8c0, src=0x7ffff7e6e1c0) at nest/rt-table.c:2348
     #6  0x000000000046468f in babel_rte_update_unreachable 
(p=p at entry=0x7ffff7e61440, e=e at entry=0x7ffff7df6e30, 
announce=announce at entry=1 '\001') at proto/babel/babel.c:698
     #7  0x0000000000466c7c in babel_rt_notify (c=<optimized out>, 
old=<optimized out>, P=0x7ffff7e61440, net=<optimized out>, new=0x0) at 
proto/babel/babel.c:2516
     #8  babel_rt_notify (P=0x7ffff7e61440, c=<optimized out>, 
net=<optimized out>, new=0x0, old=<optimized out>) at 
proto/babel/babel.c:2408
     #9  0x00000000004581b7 in rt_notify_basic 
(c=c at entry=0x7ffff7e61830, new=new at entry=0x0, 
old=old at entry=0x7ffff7d983b8) at nest/rt-table.c:1250
     #10 0x00000000004593ab in channel_notify_basic 
(_channel=0x7ffff7e61830) at nest/rt-table.c:1661
     #11 0x000000000043459b in ev_run_list_limited (l=0x53d860 
<global_work_list>, limit=9, limit at entry=10) at lib/event.c:338
     #12 0x00000000004a7f5d in io_loop () at sysdep/unix/io.c:2640
     #13 0x00000000004037d7 in main (argc=<optimized out>, 
argv=<optimized out>) at sysdep/unix/main.c:1106

Cheers, and thanks for your work!
Lars
Freifunk Berlin
-------------- next part --------------

log syslog all;
#debug protocols {states};

# Include additional bird config files for runtime extendability
# This is currently empty and not used.
include "/dev/shm/bird_*.conf";

#master4 is implicitly created
ipv6 sadr table v6_main;
ipv4 table v4_babel_ff;
ipv4 table v4_babel_default;

protocol device {
};

protocol direct {
	ipv6 sadr {
		table v6_main;
	};
	ipv4;
}

protocol babel {
	randomize router id yes;
	ipv6 sadr {
		table v6_main;
		# Import only /56 location aggregates and default routes
		import filter {
			if ! (net.len = 56 || net = ::/0 from 2001:bf7::/32) then reject;
			if ifname = "eth0.20" then {
			  babel_metric = babel_metric + 512;
			}
			if ifname = "ts_wg0" then {
			  babel_metric = babel_metric + 3072;
			}
			accept;
		};

		export filter {
			if net = 2001:bf7:750:5500::/56 from ::/0 then accept;
			if source = RTS_BABEL then accept;
			reject;
		};
	};
	ipv4 {
		import filter {
			if ifname = "eth0.20" then {
			  babel_metric = babel_metric + 512;
			}
			if ifname = "ts_wg0" then {
			  babel_metric = babel_metric + 3072;
			}
			accept;
		};
		export where source = RTS_BABEL || net ~ [ 10.0.0.0/8{21,32} ]; # Readvertise learned routes and advertise local networks from 10/8
	};

	# Mesh interfaces
	interface "eth0.20" {
		type wireless;
	};
	# Tunnel interfaces provided by tunspace
	interface "ts_wg0" {
		type wireless;
	};
}

protocol kernel {
	ipv6 sadr {
		table v6_main;
		import all;
		export all;
	};
	learn all; # Allow learning loopback route
}



# Currently not in use but keep for later purposes
protocol kernel {
	ipv4 {
		import none;
		export none;
	};
}

# TODO: Get rid of the following when OLSRD is gone
protocol kernel {
	kernel table 10;
	ipv4 {
		table v4_babel_ff;
		import none;
		export all;
	};
}

protocol pipe {
        table master4;
	peer table v4_babel_ff;
	export where net != 0.0.0.0/0;
}

protocol kernel {
	kernel table 11;
	ipv4 {
		table v4_babel_default;
		import none;
		export all;
	};
}

protocol pipe {
        table master4;
	peer table v4_babel_default;
	export where net = 0.0.0.0/0;
}