[Dnsmasq-discuss] local domain added when forwarding to upstream DNS servers

[Simon Kelley]

Lixus Zoran wrote:
> Hi,
> 
>>> That is surprising me, this querie not even gets forwarded to the upsteam server.
> 
> That is exact the bug I am complaining about.
> 
>  
>> Yes, puzzling. Try adding 'log-queries' to your /etc/dnsmasq.conf and 
>> see what gets logged when you repeat this.
> 
> 
> # nslookup lists.thekelleys.org.uk.
> Server:         127.0.0.1
> Address:        127.0.0.1#53
> ** server can't find lists.thekelleys.org.uk: REFUSED
> 
> This gets logged to /var/log/messages with log-queries enabled.
> 
>   May  4 16:14:28 mydesktop dnsmasq[8385]: query[A] lists.thekelleys.org.uk from 127.0.0.1
>   May  4 16:14:28 mydesktop dnsmasq[8385]: query[A] lists.thekelleys.org.uk from 127.0.0.1
> 
> This is what goes over the wire:
> # tshark -i any port 53
> 
>   4.827968    127.0.0.1 -> 127.0.0.1    DNS Standard query A lists.thekelleys.org.uk
>   4.828089    127.0.0.1 -> 127.0.0.1    DNS Standard query response, Refused
>   4.828383    127.0.0.1 -> 127.0.0.1    DNS Standard query A lists.thekelleys.org.uk
>   4.828448    127.0.0.1 -> 127.0.0.1    DNS Standard query response, Refused
> 
> 
> So it's very clear that dnsmasq is not forwarding to the upstream server
> instead it "refuses" the querie.
> 
> I believe it's a bug.
> 
> I ran "strace -f -p <pid of dnamasq>" while running the nslookup, not sure if this is of any help:
> 
> 8385  select(7, [3 4 5 6], [], [], NULL) = 1 (in [4])
> 8385  time(NULL)                        = 1241447007
> 8385  stat64("/etc/resolvconf/resolv.conf.d/upstream", {st_mode=S_IFREG|0644, st_size=24, ...}) = 0
> 8385  stat64("/var/run/dnsmasq/resolv.conf", {st_mode=S_IFREG|0644, st_size=21, ...}) = 0
> 8385  recvmsg(4, {msg_name(16)={sa_family=AF_INET, sin_port=htons(51220), sin_addr=inet_addr("127.0.0.1")}, msg_iov(1)=[{"\206\343\1\0\0\1\0\0\0\0\0\0\5lists\nthekelleys\3or"..., 1280}], msg_controllen=24, {cmsg_len=24, cmsg_level=SOL_IP, cmsg_type=, ...}, msg_flags=0}, 0) = 41
> 8385  ioctl(4, SIOCGIFNAME, {ifr_index=1, ifr_name="lo"}) = 0
> 8385  time(NULL)                        = 1241447007
> 8385  stat64("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2309, ...}) = 0
> 8385  write(8, "<31>May  4 16:23:27 dnsmasq[8385"..., 83) = 83
> 8385  sendmsg(4, {msg_name(16)={sa_family=AF_INET, sin_port=htons(51220), sin_addr=inet_addr("127.0.0.1")}, msg_iov(1)=[{"\206\343\201\205\0\1\0\0\0\0\0\0\5lists\nthekelleys\3o"..., 41}], msg_controllen=24, {cmsg_len=24, cmsg_level=SOL_IP, cmsg_type=, ...}, msg_flags=0}, 0) = 41
> 8385  select(7, [3 4 5 6], [], [], NULL) = 1 (in [4])
> 8385  time(NULL)                        = 1241447007
> 8385  recvmsg(4, {msg_name(16)={sa_family=AF_INET, sin_port=htons(41764), sin_addr=inet_addr("127.0.0.1")}, msg_iov(1)=[{"\310\267\1\0\0\1\0\0\0\0\0\0\5lists\nthekelleys\3or"..., 1280}], msg_controllen=24, {cmsg_len=24, cmsg_level=SOL_IP, cmsg_type=, ...}, msg_flags=0}, 0) = 41
> 8385  ioctl(4, SIOCGIFNAME, {ifr_index=1, ifr_name="lo"}) = 0
> 8385  time(NULL)                        = 1241447007
> 8385  stat64("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2309, ...}) = 0
> 8385  write(8, "<31>May  4 16:23:27 dnsmasq[8385"..., 83) = 83
> 8385  sendmsg(4, {msg_name(16)={sa_family=AF_INET, sin_port=htons(41764), sin_addr=inet_addr("127.0.0.1")}, msg_iov(1)=[{"\310\267\201\205\0\1\0\0\0\0\0\0\5lists\nthekelleys\3o"..., 41}], msg_controllen=24, {cmsg_len=24, cmsg_level=SOL_IP, cmsg_type=, ...}, msg_flags=0}, 0) = 41
> 8385  select(7, [3 4 5 6], [], [], NULL <unfinished ...>
> 
>

The only circumstances in which dnsmasq will return REFUSED wand not 
forward the query is when is  has no upstream server to forward to.

You seem to have both /etc/resolvconf/resolv.conf.d/upstream and 
/var/run/dnsmasq/resolv.conf set as resolv files but you don't mention 
the second one in your initial post. Is it possible that 
/var/run/dnsmasq/resolv.conf has a later modification time than 
/etc/resolvconf/resolv.conf.d/upstream  and is empty? That would cause 
dnsmasq to have an empty set of upstream servers, and behave in the way 
you are seeing.

Each time it reads a resolv-file dnsmasq logs the name of the file and 
the current set of servers, so it should be possible to se what's 
happening from the log.

Cheers,

Simon.