Cfrtjryk

I am compiling my own 3.14 kernel. I fear I may have left out some important networking feature to get DNS working.

I can't resolve domain names. I can ping my DNS server.
I can resolve using that DNS on other machines so I know it's not the server.

~ # cat /etc/resolv.conf

nameserver 192.168.13.5



~ # nslookup google.com

Server:    192.168.13.5

Address 1: 192.168.13.5



nslookup: can't resolve 'google.com'



~ # ping -c 1 google.com

ping: bad address 'google.com'



~ # ping -c 1 192.168.13.5 

PING 192.168.13.5 (192.168.13.5): 56 data bytes

64 bytes from 192.168.13.5: seq=0 ttl=128 time=0.382 ms



--- 192.168.13.5 ping ststistics ---

1 packets transmitted, 1 packets recieved, 0% packet loss

reound-trip min/avg/max = 0.382/0.382/0.382 ms

Any ideas what I left out? here is my config: http://pastebin.com/vt4vGTgJ

EDIT:

If it's not the kernel, what could I be missing? I am using busybox, statically linked. there are no shared libraries in this system.

The problem is with busybox. I switched to a precompiled version and did not have issues. I need to look into compilation options with it. Thanks for your help.

https://gist.github.com/vsergeev/2391575:

There are known issues with DNS functionality in statically-linked glibc programs (like busybox in this case), because libnss must be dynamically loaded. Building a uClibc toolchain and linking busybox against that would resolve this.

I ran into the same issue and it turns out that busybox is picky about the format for resolv.conf. There must be exactly one blank between the nameserver tag and the address for nslookup to work.
In addition /etc/nsswitch.conf has to include dns for host.

[ busybox master (git hash 349d72c19)
sysroot-glibc-linaro-2.25-2018.05-arm-linux-gnueabihf
]

root@4000000a:~# cat /etc/nsswitch.conf 

passwd:    files compat

shadow:    files compat

hosts:    files dns compat 

Yes the question is old, but the current busybox still behaves this way.

[ I used xxd below to show the number of blanks in resolv.conf ]

This fails:

root@4000000a:~# xxd /etc/resolv.conf

00000000: 6e61 6d65 7365 7276 6572 2020 382e 382e  nameserver  8.8.

00000010: 382e 380a                                8.8.

root@4000000a:~# nslookup  www.cnn.com 

nslookup: bad address ' 8.8.8.8'

and this works:

root@4000000a:~# xxd /etc/resolv.conf

00000000: 6e61 6d65 7365 7276 6572 2038 2e38 2e38  nameserver 8.8.8

00000010: 2e38 0a                                  .8.

root@4000000a:~# nslookup  www.cnn.com                

Server:     8.8.8.8

Address:    8.8.8.8:53



Non-authoritative answer:

www.cnn.com canonical name = turner-tls.map.fastly.net

Name:   turner-tls.map.fastly.net

Address: 151.101.1.67

Name:   turner-tls.map.fastly.net

Address: 151.101.65.67

Name:   turner-tls.map.fastly.net

Address: 151.101.129.67

Name:   turner-tls.map.fastly.net

Address: 151.101.193.67



Non-authoritative answer:

www.cnn.com canonical name = turner-tls.map.fastly.net

Name:   turner-tls.map.fastly.net

Address: 2a04:4e42::323

Name:   turner-tls.map.fastly.net

Address: 2a04:4e42:200::323

Name:   turner-tls.map.fastly.net

Address: 2a04:4e42:400::323

Name:   turner-tls.map.fastly.net

Address: 2a04:4e42:600::323

I'm not sure if this is the same problem I had or not, but I recently upgraded and old internal DNS server system from OpenBSD 3.8 to 5.6, and I lost the ability to resolve hosts with ping, but the host command was working. Turned out I had to add 127.0.0.1/8 to the match-clients directive in named in addition to the 192.168.0.0/16 which I already had there, and then it started to work properly after restarting named.

I had the same problem. I've used buildroot to build the filesystem, to compile the kernel and to add extra packages with busybox.

I was only able to ping an ip address. With url the ping command returned: bad address error. Then I changed the resolv.conf file.

sudo vim /etc/resolv.conf



nameserver gateway_ip_address

nameserver 8.8.8.8

nameserver 8.8.4.4

And everything worked fine.

I resolved the same symptoms by editing: /etc/nsswitch.conf and adding DNS to the following line:

hosts:      files dns

sudo vim /etc/resolv.conf to edit resolv.conf, make sure nameserver addresses (as well as the keyword 'nameserver') are separated by a single space, not a comma, like below:

nameserver 8.8.8.8 8.8.4.4