OPNsense firewall on Proxmox fix ‘no internet’

Giovanni — Sat, 17 Nov 2018 18:17:25 +0000

Quick post to note how I determined and then fixed the internet access issue I was having when I installed OPNsense on Proxmox.

OPNsense virtual machine is configured with VirtiO network drivers.

Other than the obvious “I can’t access anything on the internet” or can’t reach external IP addresses problem I looked at troubleshooting via nmap – because the devices on the network could ping externally (8.8.8.8) and also resolve DNS requests.

In a broken state you may see ‘tcpwrapper’ when testing a known host serving HTTP, like so:

root@test:~# nmap -p 80 -sV 216.58.194.206

Starting Nmap 7.40 ( https://nmap.org ) at 2018-11-17 17:54 UTC

Nmap scan report for sfo03s01-in-f206.1e100.net (216.58.194.206)

Host is up (0.010s latency).

PORT STATE SERVICE VERSION

80/tcp open tcpwrapped

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .

Nmap done: 1 IP address (1 host up) scanned in 7.91 seconds

To fix this issue, ensure that “Disable hardware checksum offload” is enabled in the OPNsense interface, then reboot the firewall for changes to take effect.

After a reboot, doing another test via nmap will actually respond with HTTP fingerprints, as expected and internet is back.

root@test:~# nmap -p 80 -sV 216.58.194.206

Starting Nmap 7.40 ( https://nmap.org ) at 2018-11-17 18:00 UTC

Nmap scan report for sfo03s01-in-f14.1e100.net (216.58.194.206)

Host is up (0.0096s latency).

PORT STATE SERVICE VERSION

80/tcp open http gws

1 service unrecognized despite returning data. If you know the service/version, please submit the following fingerprint at https://nmap.org/cgi-bin/submit.cgi?new-service :

SF-Port80-TCP:V=7.40%I=7%D=11/17%Time=5BF0574C%P=x86_64-pc-linux-gnu%r(Get

SF:Request,8A7A,"HTTP/1\.0\x20200\x20OK\r\nDate:\x20Sat,\x2017\x20Nov\x202

SF:018\x2018:00:43\x20GMT\r\nExpires:\x20-1\r\nCache-Control:\x20private,\

SF:x20max-age=0\r\nContent-Type:\x20text/html;\x20charset=ISO-8859-1\r\nP3

SF:P:\x20CP=\"This\x20is\x20not\x20a\x20P3P\x20policy!\x20See\x20g\.co/p3p

SF:help\x20for\x20more\x20info\.\"\r\nServer:\x20gws\r\nX-XSS-Protection:\

SF:x201;\x20mode=block\r\nX-Frame-Options:\x20SAMEORIGIN\r\nSet-Cookie:\x2

SF:01P_JAR=2018-11-17-18;\x20expires=Mon,\x2017-Dec-2018\x2018:00:43\x20GM

SF:T;\x20path=/;\x20domain=\.google\.com\r\nSet-Cookie:\x20NID=146=0dp1WLb

SF:UhFIr1MIVwhAglx_4O6x-0eJHrmYFTov9a3oFxE2-lZSUI_9mmKBFXQZjYbjKbSRiirLZ-U

SF:cfybTiNQR_vmHD2MY4RBHP-hj4K7oyQX4lXuCgrSU7ESRXiX2Jn0qwoLWvvEItnC2hgDHEb

SF:oLJffQrfiEazdGDp5XppPU;\x20expires=Sun,\x2019-May-2019\x2018:00:43\x20G

SF:MT;\x20path=/;\x20domain=\.google\.com;\x20HttpOnly\r\nAccept-Ranges:\x

SF:20none\r\nVary:\x20Accept-Encoding\r\n\r\n

SF:emscope=\"\"\x20itemtype=\"http://schema\.org/WebPage\"\x20lang=\"en\">

SF:

SF:cluding\x20webpages,\x20images,\x20videos\x20and\x20more\.\x20Google\x2

SF:0has\x20ma")%r(HTTPOptions,71B,"HTTP/1\.0\x20405\x20Method\x20Not\x20Al

SF:lowed\r\nAllow:\x20GET,\x20HEAD\r\nDate:\x20Sat,\x2017\x20Nov\x202018\x

SF:2018:00:44\x20GMT\r\nContent-Type:\x20text/html;\x20charset=UTF-8\r\nSe

SF:rver:\x20gws\r\nContent-Length:\x201592\r\nX-XSS-Protection:\x201;\x20m

SF:ode=block\r\nX-Frame-Options:\x20SAMEORIGIN\r\n\r\n\n

SF:\n\x20\x20\n\x20\x20

SF:me=viewport\x20content=\"initial-scale=1,\x20minimum-scale=1,\x20width=

SF:device-width\">\n\x20\x20Error\x20405\x20\(Method\x20Not\x20Allo</span></code></p> <p class="p1"><code><span class="s1">SF:wed\)!!1\n\x20\x20

opnsense – Giovanni F. Mazzeo De Santolo

OPNsense firewall on Proxmox fix ‘no internet’