tests: filter out non-ICMP packets in the tun test

[evverx]

When systemd-resolved with its LLMNR/mDNS responders enabled is run it starts sending its probes as soon as the tun interface pops up:

00:36:36.643708 IP c > igmp.mcast.net: igmp v3 report, 2 group record(s)
00:36:36.644530 IP c.mdns > mdns.mcast.net.mdns: 0 [1n] ANY (QM)? c.local. (44)
00:36:36.645307 IP c.llmnr > 224.0.0.252.llmnr: UDP, length 22

and that interferes with the test. Since the test is interested in ICMP packets only it can safely skip everything else.

Fixes:

 #(006)=[failed] Send ping packets from Linux into Scapy
 ...
 assert len(icmp4_sequences) == 3
 AssertionError

(The tap test seems to fail too but as far as I can see it has something to do with cd01ec1 (according to git bisect). I'll try to take a closer look later. As far as I can tell src candidates in conf.route6 are different from what the test expects there)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.61%. Comparing base (1f9061d) to head (856fc91).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4543      +/-   ##
==========================================
+ Coverage   81.24%   81.61%   +0.37%     
==========================================
  Files         356      356              
  Lines       85533    85533              
==========================================
+ Hits        69491    69808     +317     
+ Misses      16042    15725     -317     

see 19 files with indirect coverage changes

[gpotter2]

Nice catch ! Thanks

[evverx]

The tap test seems to fail too but as far as I can see it has something to do with cd01ec1 (according to git bisect)

Looks like it could have been caught by the CI if it had run the IPv6 tests: https://github.com/evverx/scapy/actions/runs/11134596243/job/30943071529?pr=2

Here's what conf.route6 looks like with the master branch (where the test fails):

2024-10-01T22:29:56.1737307Z Destination                  Next Hop  Iface  Src candidates             Metric
2024-10-01T22:29:56.1737973Z ::1/128                      ::        lo     ::1                        0     
2024-10-01T22:29:56.1738645Z 2001:db8::1/128              ::        tun0   2001:db8::2                0     
2024-10-01T22:29:56.1739262Z fe80::6245:bdff:feee:423d/_  ::        eth0   fe80::6245:bdff:feee:423d  0     
2024-10-01T22:29:56.1739926Z fe80::8208:2d66:c4fb:3987/_  ::        tun0   fe80::8208:2d66:c4fb:3987  0     
2024-10-01T22:29:56.1740607Z ::1/128                      ::        lo     ::1                        256   
2024-10-01T22:29:56.1741424Z 2001:db8::1/128              ::        tun0   2001:db8::2                256   
2024-10-01T22:29:56.1742015Z 2001:db8::2/128              ::        tun0   2001:db8::2                256   
2024-10-01T22:29:56.1742658Z fe80::/64                    ::        eth0   fe80::6245:bdff:feee:423d  256   
2024-10-01T22:29:56.1743226Z fe80::/64                    ::        tun0   fe80::8208:2d66:c4fb:3987  256   
2024-10-01T22:29:56.1743763Z ff00::/8                     ::        eth0   fe80::6245:bdff:feee:423d  250   
2024-10-01T22:29:56.1744364Z ff00::/8                     ::        tun0   2001:db8::2                250   
2024-10-01T22:29:56.1744903Z                                               fe80::8208:2d66:c4fb:3987        
2024-10-01T22:29:56.1745220Z 

Here's what it looks like without cd01ec1 (where the test passes):

2024-10-01T22:42:27.5093454Z Destination                  Next Hop  Iface  Src candidates             Metric
2024-10-01T22:42:27.5094391Z 2001:db8::1/128              ::        tun0   2001:db8::1                256   
2024-10-01T22:42:27.5095307Z 2001:db8::2/128              ::        tun0   2001:db8::1                256   
2024-10-01T22:42:27.5096165Z fe80::/64                    ::        eth0   fe80::20d:3aff:fed4:567b   256   
2024-10-01T22:42:27.5096977Z fe80::/64                    ::        tun0   fe80::4cbf:cb15:d001:d665  256   
2024-10-01T22:42:27.5097768Z ::1/128                      ::        lo     ::1                        0     
2024-10-01T22:42:27.5098521Z 2001:db8::1/128              ::        tun0   2001:db8::1                0     
2024-10-01T22:42:27.5099447Z fe80::20d:3aff:fed4:567b/1_  ::        eth0   fe80::20d:3aff:fed4:567b   0     
2024-10-01T22:42:27.5100391Z fe80::4cbf:cb15:d001:d665/_  ::        tun0   fe80::4cbf:cb15:d001:d665  0     

As far as can tell the test fails because 2001:db8::1 is no longer among the src candidates so src is 2001:db8::2 where 2001:db8::1 is expected.

<IPv6  version=6 tc=0 fl=0 plen=8 nh=ICMPv6 hlim=64 src=2001:db8::2 dst=2001:db8::2 |<ICMPv6EchoRequest  type=Echo Request code=0 cksum=0x2446 id=0x0 seq=0x1 data=b'' |>>
<IPv6  version=6 tc=0 fl=0 plen=8 nh=ICMPv6 hlim=64 src=2001:db8::2 dst=2001:db8::2 |<ICMPv6EchoRequest  type=Echo Request code=0 cksum=0x2445 id=0x0 seq=0x2 data=b'' |>>
<IPv6  version=6 tc=0 fl=0 plen=8 nh=ICMPv6 hlim=64 src=2001:db8::2 dst=2001:db8::2 |<ICMPv6EchoRequest  type=Echo Request code=0 cksum=0x2444 id=0x0 seq=0x3 data=b'' |>>

I'll take a closer look a bit later.