[Dnsmasq-discuss] No more random source port

Risto Suominen risto.suominen at gmail.com
Wed Mar 22 16:30:56 GMT 2017


Hi Albert,

2017-03-21 22:47 UTC+02.00, Albert ARIBAUD <albert.aribaud at free.fr>:
>
> I can't see why your dnsmasq would only use one port. This would be the
> behavior for -Q0 (or -Q45807, but your dnsmasq does not have this option
> in its command line.
>
I took in the source package and added some log entries (from syslog):

Mar 20 22:11:59 risto-Macmini dnsmasq[30248]: main: port=53
Mar 20 22:11:59 risto-Macmini dnsmasq[30248]: pre_allocate_sfds: query_port=0
Mar 20 22:11:59 risto-Macmini dnsmasq[30248]: started, version 2.75
cache disabled
Mar 20 22:11:59 risto-Macmini dnsmasq[30248]: compile time options:
IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua TFTP conntrack ipset
auth DNSSEC loop-detect inotify
Mar 20 22:11:59 risto-Macmini dnsmasq[30248]: DBus support enabled:
connected to system bus
Mar 20 22:11:59 risto-Macmini dnsmasq[30248]: warning: no upstream
servers configured
Mar 20 22:12:00 risto-Macmini dnsmasq[30248]: setting upstream servers from DBus
Mar 20 22:12:00 risto-Macmini dnsmasq[30248]: check_servers: flags=90
Mar 20 22:12:00 risto-Macmini dnsmasq[30248]: check_servers: sfd=(nil) (before)
Mar 20 22:12:00 risto-Macmini dnsmasq[30248]: check_servers:
sfd=0x555fbb7955a0 (after)
Mar 20 22:12:00 risto-Macmini dnsmasq[30248]: using nameserver
8.8.8.8#53(via eth0)

This shows that the 'sfd' is allocated in function 'check_servers' (in
file 'network.c'). This file descriptor is used later to send the
forwarded queries. It can be seen in 'netstat -ln --inet':

udp        0      0 0.0.0.0:45807           0.0.0.0:*

> Did you check apparmor or SELinux?
>
No. How should I do that?

Risto



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