Hello everyone.
Today I have returned to work, where I am running dnsmasq 2.89 on my
Fedora 27 laptop. It is configured by Network Manager by its dns=dnsmasq
plugin. But when I returned today, I have found our internal network
refused to resolve any name. I dug into dnsmasq what it does. Problem is
it did not fix itself after a while, but stubbornly failed without later
fix.
It were failing quite often on random_sock() local_bind call. The errno
returned 99. I have noticed it failed to notice change of ifindex in
interface it should be bound to.
(gdb) bt
#0 0x00007f53305e7020 in strerror () from /lib64/libc.so.6
#1 0x00005557a3ec2c4b in random_sock (s=s@entry=0x5557a43fef50) at
/usr/src/debug/dnsmasq-2.89-5.fc37.x86_64/src/forward.c:2511
#2 0x00005557a3ec62f2 in allocate_rfd (fdlp=fdlp@entry=0x5557a43f5280,
serv=serv@entry=0x5557a43fef50)
at /usr/src/debug/dnsmasq-2.89-5.fc37.x86_64/src/forward.c:2607
#3 0x00005557a3ec72dc in forward_query (udpfd=4,
udpaddr=0x7ffdb6bfbd30, dst_addr=0x7ffdb6bfbd00, dst_iface=0,
header=0x5557a43e03d0, plen=51,
limit=0x5557a43e0880 "", now=1697453089, forward=0x5557a43f5230,
ad_reqd=1, do_bit=0, fast_retry=0)
at /usr/src/debug/dnsmasq-2.89-5.fc37.x86_64/src/forward.c:498
#4 0x00005557a3ed0ebd in receive_query (now=1697453089,
listen=0x5557a43e0cc0) at
/usr/src/debug/dnsmasq-2.89-5.fc37.x86_64/src/forward.c:1869
#5 check_dns_listeners (now=1697453089) at
/usr/src/debug/dnsmasq-2.89-5.fc37.x86_64/src/dnsmasq.c:1845
#6 0x00005557a3eac9ef in main (argc=<optimized out>, argv=<optimized
out>) at /usr/src/debug/dnsmasq-2.89-5.fc37.x86_64/src/dnsmasq.c:1266
(gdb) p *$d->servers->next->next->next->next->next->next
$8 = {flags = 800, domain_len = 14, domain = 0x5557a43f5eb0
"brq.redhat.com", next = 0x5557a43ffa10, serial = 6, arrayposn = 23,
last_server = -1, addr = {sa = {sa_family = 2, sa_data =
"\0005\n&\005\032\226\r\2170S\177\000"}, in = {sin_family = 2, sin_port
= 13568,
sin_addr = {s_addr = 436545034}, sin_zero =
"\226\r\2170S\177\000"}, in6 = {sin6_family = 2, sin6_port = 13568,
sin6_flowinfo = 436545034,
sin6_addr = {__in6_u = {__u6_addr8 =
"\226\r\2170S\177\000\0000\275\001\a\220\000\000", __u6_addr16 = {3478,
12431, 32595, 0, 48432, 1793,
144, 0}, __u6_addr32 = {814681494, 32595, 117554480,
144}}}, sin6_scope_id = 3446832640}}, source_addr = {sa = {sa_family = 2,
sa_data = "\000\000\000\000\000\000@\274\277\266\375\177\000"},
in = {sin_family = 2, sin_port = 0, sin_addr = {s_addr = 0},
sin_zero = "@\274\277\266\375\177\000"}, in6 = {sin6_family = 2,
sin6_port = 0, sin6_flowinfo = 0, sin6_addr = {__in6_u = {
__u6_addr8 =
"@\274\277\266\375\177\000\000@\274\277\266\375\177\000", __u6_addr16 =
{48192, 46783, 32765, 0, 48192, 46783, 32765, 0},
__u6_addr32 = {3066018880, 32765, 3066018880, 32765}}},
sin6_scope_id = 814672583}},
interface = "enp9s0u1\000\000\000\000\000\000\000\000", ifindex = 7,
sfd = 0x0, tcpfd = 0, edns_pktsz = 1232, pktsz_reduced = 0, queries = 446,
failed_queries = 0, nxdomain_replies = 0, retrys = 4, query_latency =
0, mma_latency = 0, forwardtime = 0, forwardcount = 0, uid = 3867576473}
(gdb) p *$d->servers->next->next->next->next->next->next->next
$9 = {flags = 800, domain_len = 10, domain = 0x5557a43ff9f0
"redhat.com", next = 0x5557a43f5fb0, serial = 7, arrayposn = 25,
last_server = -1,
addr = {sa = {sa_family = 2, sa_data =
"\0005\n&\005\032\226\r\2170S\177\000"}, in = {sin_family = 2, sin_port
= 13568, sin_addr = {
s_addr = 436545034}, sin_zero = "\226\r\2170S\177\000"}, in6 =
{sin6_family = 2, sin6_port = 13568, sin6_flowinfo = 436545034,
sin6_addr = {__in6_u = {__u6_addr8 =
"\226\r\2170S\177\000\0000\275\001\a\220\000\000", __u6_addr16 = {3478,
12431, 32595, 0, 48432, 1793,
144, 0}, __u6_addr32 = {814681494, 32595, 117554480,
144}}}, sin6_scope_id = 3446832640}}, source_addr = {sa = {sa_family = 2,
sa_data = "\000\000\000\000\000\000@\274\277\266\375\177\000"},
in = {sin_family = 2, sin_port = 0, sin_addr = {s_addr = 0},
sin_zero = "@\274\277\266\375\177\000"}, in6 = {sin6_family = 2,
sin6_port = 0, sin6_flowinfo = 0, sin6_addr = {__in6_u = {
__u6_addr8 =
"@\274\277\266\375\177\000\000@\274\277\266\375\177\000", __u6_addr16 =
{48192, 46783, 32765, 0, 48192, 46783, 32765, 0},
__u6_addr32 = {3066018880, 32765, 3066018880, 32765}}},
sin6_scope_id = 814672583}},
interface = "enp9s0u1\000\000\000\000\000\000\000\000", ifindex = 6,
sfd = 0x0, tcpfd = 0, edns_pktsz = 1232, pktsz_reduced = 0,
queries = 6480, failed_queries = 0, nxdomain_replies = 0, retrys =
134, query_latency = 34, mma_latency = 4414, forwardtime = 0,
forwardcount = 0, uid = 3578949556}
$ ip a show dev enp9s0u1
7: enp9s0u1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel
state UP group default qlen 1000
link/ether 00:50:b6:b4:17:b2 brd ff:ff:ff:ff:ff:ff
inet 10.43.2.229/24 brd 10.43.2.255 scope global dynamic
noprefixroute enp9s0u1
valid_lft 56729sec preferred_lft 56729sec
inet6 2620:52:0:2b02:b3ba:7320:65f8:1fff/64 scope global dynamic
noprefixroute
valid_lft 2591999sec preferred_lft 604799sec
inet6 fe80::b2f:65c5:d743:524b/64 scope link noprefixroute
valid_lft forever preferred_lft forever
The problem seems to be wrong ifindex for redhat.com domain, while for
brq.redhat.com it has refreshed correctly. I am not sure how exactly did
that happen, but I think I have saw that few times already. I am not
sure about exact steps required to reproduce this issue, but I think it
would be related to undocking from thunderbolt and reconnecting again.
Has anyone else saw similar behaviour?
It seems to me call to enumerate_interfaces(0) should have fixed this. I
wonder whether it would make sense to call it explicitly after
local_bind failure. Because full journal I do not have details about
interface changes anymore:
journalctl -xeu NetworkManager | grep 'failed to bind server socket to
enp9s0u1' | wc -l
711
Has similar error been seen in the wild? Is there fix for it, which I
have failed to find?
Cheers,
Petr
--
Petr Menšík
Software Engineer, RHEL
Red Hat, http://www.redhat.com/
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB
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