Re: [MirageOS-devel] Problem http reply with mirage-static and mirage-www

[Thomas Leonard <talex5@xxxxxxxxx>]

On 7 June 2015 at 16:25, Richard Mortier <richard.mortier@xxxxxxxxxxxx> wrote:
> On 7 June 2015 at 16:11, Carlos Oviedo <luis.oviedogc@xxxxxxxxx> wrote:
>>> The first ACK of the unseen segment looks really weird to me -- did
>>> wireshark report drops? What version of mirage-tcpip are you using? If
>>> the latest, might be worth trying to back off (via opam pin) as
>>> there've been changes recently that may be having subtle effects...
>>
>> Wireshark reports unseen ACKed unseen segments and duplicated acks,
>> wondering if it is only me who sees this weird behaviour.
>> Using the latest version (2.4.3), will try as suggested.
>>
>>> (Possibly also easier for others to read if you just capture a binary
>>> .pcap file and attach that -- quite hard to parse the text output in
>>> an email like that, for me at least!)
>>
>> Attached :)
>
> Hm-- the ACK that completes the handshake appears to have the spurious
> trailing 6 zero bytes. Because these 6 bytes aren't expected, they're
> not actually given in the sequence number space (sent in a segment
> from .104 with ACK=true, seqno=1, ackno=1), and so when the server
> (.114) explicitly ACKs (ACK=true, seqno=1, ackno=7) them, things
> subsequently get confused with duplicate ACKs, apparently spurious
> retransmissions, etc.
>
> This is a bit weird because the client is CURL which one assumes is
> using the local stack which ought to be roughly correct (!)
>
> Carlos-- what exactly is the experimental setup here -- hosts, VMs, IP
> addresses, kernel versions, etc?
>
> Thomas, Dave, Balraj-- should Mirage be ACKing these spurious bytes
> (one assumes not even if they're included)?  But any ideas why they're
> included at all -- is this a Xen issue?!

I don't know why they're included, but here's a patch to remove them
(already applied to master):

https://github.com/mirage/mirage-tcpip/pull/145


-- 
Dr Thomas Leonard        http://roscidus.com/blog/
GPG: DA98 25AE CAD0 8975 7CDA  BD8E 0713 3F96 CA74 D8BA

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