[Chilli] [PATCH] Issue with EDNS

[Michele Bergonzoni]

I have a patch to submit for dealing with EDNS requests.

I am trying to setup a layer3-only environment, and in my tests I got 
inconsistent results, some clients working and some other not working.

I discovered that a PC with a brand-new freshly-installed ubuntu, 
querying a DNS server with bind 9.8.4 (debian 7.2) consistently fails to 
receive a DNS answer, with a "Record type 41" debug message. No DNS 
means no redirection, no login page, just browser error.

Record type 41 is a pseudo record used in EDNS requests. So I am now 
using this patch (relative to svn revision 485):

Index: src/dns.c
===================================================================
--- src/dns.c   (revision 485)
+++ src/dns.c   (working copy)
@@ -360,6 +360,7 @@
      break;
    case 29: log_dbg("LOC record"); break;
    case 33: log_dbg("SRV record"); break;
+  case 41: log_dbg("EDNS OPT pseudorecord"); break;
    case 47: log_dbg("NSEC record"); break;
    }

This patch makes my client happy and working with many sites (all the 
sites that I tried), but Coovachilli's code is complex and EDNS is 
complex as well, so I am not really sure that this is the right thing to do.

In fact I am almost sure that this isn't a proper EDNS support, because 
the command (a standard test for EDNS):

dig tcf.rs.dns-oarc.net txt

fails (timeouts) on the connected client, and works on the chilli 
machine. When the client tries it, the debug says (previous patch applied):

dhcp.c: 5020: 0 (Debug) dhcp_decaps: src=<MAC of first router fronting 
chilli's DHCP interface> dst=<mac of chilli's DHCP interface> prot=0800 
2048 len=90
dhcp.c: 3551: 0 (Debug) function dhcp_receive_ip()
dhcp.c: 238: 0 (Debug) Looking up appconn for 198.18.253.1 (IP of client 
machine)
dhcp.c: 1703: 0 (Debug) dhcp_dns plen=90 dlen=36 olen=36
dhcp.c: 1704: 0 (Debug) DNS ID:    40833
dhcp.c: 1705: 0 (Debug) DNS Flags: 256
dns.c: 156: 0 (Debug) dns_copy_res: left=36 olen=36 qsize=512
dns.c: 40: 0 (Debug) dns_fullname dlen=1499 reslen=36 olen=36 lvl=0
dns.c: 80: 0 (Debug) part[tcf] reslen=35 l=3 dlen=1499
dns.c: 80: 0 (Debug) part[rs] reslen=31 l=2 dlen=1495
dns.c: 80: 0 (Debug) part[dns-oarc] reslen=28 l=8 dlen=1492
dns.c: 80: 0 (Debug) part[net] reslen=19 l=3 dlen=1483
dns.c: 187: 0 (Debug) It was a dns record type: 16 class: 1
dns.c: 40: 0 (Debug) dns_fullname dlen=512 reslen=36 olen=36 lvl=0
dns.c: 80: 0 (Debug) part[tcf] reslen=35 l=3 dlen=512
dns.c: 80: 0 (Debug) part[rs] reslen=31 l=2 dlen=508
dns.c: 80: 0 (Debug) part[dns-oarc] reslen=28 l=8 dlen=505
dns.c: 80: 0 (Debug) part[net] reslen=19 l=3 dlen=496
dns.c: 194: 0 (Debug) DNS: tcf.rs.dns-oarc.net
dns.c: 156: 0 (Debug) dns_copy_res: left=11 olen=36 qsize=512
dns.c: 40: 0 (Debug) dns_fullname dlen=1499 reslen=11 olen=36 lvl=0
dns.c: 187: 0 (Debug) It was a dns record type: 41 class: 4096
dns.c: 280: 0 (Debug) -> w ttl: 0 rdlength: 0/0
dns.c: 363: 0 (Debug) EDNS OPT pseudorecord
dhcp.c: 1787: 0 (Debug) left (should be zero): 0 q=tcf.rs.dns-oarc.net
dhcp.c: 238: 0 (Debug) Looking up appconn for 198.18.253.1
tun.c: 1089: 0 (Debug) tun_encaps(tun0) len=76
tun.c: 802: 0 (Debug) tun_decaps(idx=0, len=1500)
chilli.c: 2664: 0 (Debug) invalid UDP packet 1500 / 4062 / 1500
tun.c: 802: 0 (Debug) tun_decaps(idx=0, len=1500)
chilli.c: 2664: 0 (Debug) invalid UDP packet 1500 / 29494 / 1500
tun.c: 802: 0 (Debug) tun_decaps(idx=0, len=1122)
chilli.c: 2677: 0 (Debug) sending to : 198.18.253.1
dhcp.c: 5376: 0 (Debug) adding 14 to IP frame length 1136
dhcp.c: 238: 0 (Debug) Looking up appconn for 198.18.253.1
dhcp.c: 411: 0 (Debug) dhcp_send() len=1136

I really don't know if this can be a real issue in a production 
environment or is just a overzaelous test, but hope this helps somehow.

BTW, I found that if I use the chilli machine as a DNS resolver, I have 
to use the WAN IP address and not the DHCP interface IP address, that 
gives only UDP port unreachable on UDP 53. Since the workaround is so 
straightforward, I didnt' test and dig this very much.

Best regards and thanks everybody for your patience,

			Bergonz

-- 
Ing. Michele Bergonzoni - Laboratori Guglielmo Marconi S.p.a.
Phone:+39-051-6781926 e-mail: bergonz at labs.it
alt.advanced.networks.design.configure.operate