[squid-users] Empty transfer-encoding header causes 502 response

Wed Oct 26 00:55:20 UTC 2022

Hi all,

Thanks for the replies.

I have included the requested output from tcpdump below:

 tcpdump -A -s 0 -ni enp4s0 "host 159.203.14.9 and (((ip[2:2] -
((ip[0]&0xf)<<2)) - ((tcp[12]&
0xf0)>>2)) != 0)"
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on enp4s0, link-type EN10MB (Ethernet), snapshot length 262144
bytes

01:40:17.310479 IP 10.0.160.10.43426 > 159.203.14.9.1996: Flags [P.], seq
2955630477:2955630939, ack 2382737005, win 502, options [nop,nop,TS val
3000375654 ecr 1932743995], length 462
E....:@.?.7.
..
...     .....+W....m....Y......
...fs3U;GET http://nintendo.com/ HTTP/1.1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:106.0)
Gecko/20100101 Firefox/106.0
Accept:
text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8
Accept-Language: en-GB,en;q=0.5
Accept-Encoding: gzip, deflate
Upgrade-Insecure-Requests: 1
Host: nintendo.com
Via: 1.1 dce3749b9671 (squid/5.6)
X-Forwarded-For: 10.0.130.210
Cache-Control: max-age=259200
Connection: keep-alive

01:40:18.957475 IP 159.203.14.9.1996 > 10.0.160.10.43426: Flags [P.], seq
1:1466, ack 462, win 114, options [nop,nop,TS val 1932744407 ecr
3000375654], length 1465
E....@@.3......
..
.......m.+Y[...r]......
s3V....fHTTP/1.1 200 OK
x-powered-by: Express
content-type: text/html; charset=iso-8859-1
transfer-encoding:
date: Wed, 26 Oct 2022 00:40:20 GMT
connection: close

<!DOCTYPE html PUBLIC "-//IETF//DTD HTML 2.0//EN"><html><head>
<!-- this automatically loads the hallway after 20 seconds -->
<meta http-equiv="refresh" content="20; url=
http://nintendo.com//./hallway/index.html">
<title>Nintendo Power Source</title>

On Tue, Oct 25, 2022 at 2:08 PM Alex Rousskov <
rousskov at measurement-factory.com> wrote:

> On 10/23/22 20:36, Matthew H wrote:
> > Hi,
> >
> > I'm using Squid to proxy HTTP requests to another proxy. I can see squid
> > sending the request to the parent and getting a response, but it sends
> > the client that initiated the request a 502 Bad Gateway response.
> >
> > On closer inspection it appears the parent proxy is sending an
> > empty transfer-encoding header, and this is causing Squid to send a 502.
>
> Do you know whether the response body was using chunked (or any other
> non-identity) encoding? I have already added your case to the list of
> known rejected responses[1], but it would be good to update that with
> the information on the actual response encoding.
>
> [1] https://github.com/squid-cache/squid/pull/702#issuecomment-762459132
>
> If the very first bytes of the response are "<html" or similar, then no
> encoding was probably applied. If you see what can be interpreted as a
> small hex number followed by a new line, then chunked encoding was
> probably applied (at least). If you cannot tell, or are not sure, feel
> free to share the response packet in libpcap format, captured with
> wireshark or "tcpdump -s0".
>
>
> Thank you,
>
> Alex.
>
>
>
> > 2022/10/24 00:23:59.106| ctx: enter level  0: 'http://nintendo.com/
> > <http://nintendo.com/>'
> > 2022/10/24 00:23:59.106| 11,3| http.cc(666) processReplyHeader:
> > processReplyHeader: key '19010000000000000C00000000000000'
> > 2022/10/24 00:23:59.106| 11,2| http.cc(720) processReplyHeader: HTTP
> > Server conn294 local=172.25.0.3:57802
> > <http://172.25.0.3:57802/> remote=159.203.14.9:1996
> > <http://159.203.14.9:1996/> FIRSTUP_PARENT FD 26 flags=1
> > 2022/10/24 00:23:59.106| 11,2| http.cc(721) processReplyHeader: HTTP
> > Server RESPONSE:
> > ---------
> > HTTP/1.1 200 OK
> > x-powered-by: Express
> > content-type: text/html; charset=iso-8859-1
> > transfer-encoding:
> > date: Mon, 24 Oct 2022 00:23:57 GMT
> > connection: close
> >
> > ----------
> > 2022/10/24 00:23:59.106| 55,3| HttpHeader.cc(882) getList: empty list
> > header: Transfer-Encoding(Transfer-Encoding[63])
> > 2022/10/24 00:23:59.106| 55,2| HttpHeader.cc(559) parse: WARNING:
> > unsupported Transfer-Encoding used by client:
> > 2022/10/24 00:23:59.106| ctx: exit level  0
> > 2022/10/24 00:23:59.106| 20,3| store.cc(1673) reset:
> > http://nintendo.com/ <http://nintendo.com/>
> > 2022/10/24 00:23:59.107| 17,3| FwdState.cc(492) fail: ERR_INVALID_RESP
> > "Bad Gateway"
> > http://nintendo.com/ <http://nintendo.com/>
> > 2022/10/24 00:23:59.107| 17,3| FwdState.cc(533) unregister:
> > http://nintendo.com/ <http://nintendo.com/>
> >
> > _______________________________________________
> > squid-users mailing list
> > squid-users at lists.squid-cache.org
> > http://lists.squid-cache.org/listinfo/squid-users
>
> _______________________________________________
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