Networking looks OK, but does not work at all

Question

I am trying to get networking to work on Sabayon X KDE Edition. I have configured wireless networking using the NetworkManager applet and networking looks OK.

However, I can't connect to the Internet, I cannot ping my gateway and I cannot even ping localhost. I have never seen this behaviour on Linux.

I am using a manually-configured kernel because I have to boot using UEFI. If you suspect any specific Kernel options, I can check them against the config. Also, networking worked fine in the Sabayon live environment.

Does anybody have an idea what is going on here?

# ifconfig
lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 0  (Lokale Schleife)
        RX packets 66  bytes 5208 (5.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 66  bytes 5208 (5.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.178.36  netmask 255.255.255.0  broadcast 192.168.    178.255
        inet6 fe80::c685:8ff:fe30:b77c  prefixlen 64  scopeid 0x20<link>
        ether c4:85:08:30:b7:7c  txqueuelen 1000  (Ethernet)
        RX packets 402  bytes 44048 (43.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 169  bytes 73070 (71.3 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

# netstat -r
Kernel IP Routentabelle
Ziel            Router          Genmask         Flags   MSS Fenster irtt     Iface
default         192.168.178.1   0.0.0.0         UG        0 0          0     wlan0
loopback        localhost       255.0.0.0       UG        0 0          0     lo
192.168.178.0   *               255.255.255.0   U         0 0          0     wlan0

# ping -c3 192.168.178.36
PING 192.168.178.36 (192.168.178.36) 56(84) bytes of data.

--- 192.168.178.36 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2007ms

# ping -c3 localhost
PING localhost (127.0.0.1) 56(84) bytes of data.

--- localhost ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2005ms

Since I can't answer my own question because I do not have enough reputation on this stackexchange (yet): I found the root cause. I'll share it here for anyone who hits the same problem. The problem was that Sabayon ships with ufw (a firewall, it seems) per default. For some unknown reason, this failed to initialize properly. Doing # rc-update del ufw and rebooting fixed the issue for me. — Jannik Jochem, Dec 28 '12 at 15:54
Interesting, I was always under the pretense that pinging loopback only tested the TCP/IP stack and should be ignored by firewalls. — JZeolla, Dec 28 '12 at 17:29
@SteelCityHacker Indeed, a well-configured firewall would not block ping (to localhost or elsewhere). Jannik's problem was that the firewall was not initialized properly. — Gilles 'SO- stop being evil', Dec 28 '12 at 23:12
Future visitors: If this happens to you and it is not a firewall issue, check that `ip rule` has a `from all lookup local` line, preferably at the top. If not, something on your system (or yourself, by running `ip rule del`) botched that. Use `ip rule add table local prio 0` to fix. (Yes, i'm speaking from experience). And by the way, `ifconfig` and `netstat -r` are deprecated on Linux. Use `ip addr` and `ip route` instead. — BatchyX, May 31 '13 at 08:21

score 3 · Answer 1 · edited Jun 18 '16 at 13:03

From OP's comment:

I found the root cause. I'll share it here for anyone who hits the same problem. The problem was that Sabayon ships with ufw (a firewall, it seems) per default. For some unknown reason, this failed to initialize properly. Doing # rc-update del ufw and rebooting fixed the issue for me. – Jannik Jochem Dec 28 '12 at 15:54

With this, the question is effectively answered (and, as a side-effect, removed from Unanswered Questions queue).

Networking looks OK, but does not work at all

1 Answers1