Re: scp dropping connections

[Sad Clouds <cryintothebluesky%googlemail.com@localhost>]

On Fri, 8 Apr 2016 12:03:43 +0000 (UTC)
christos%astron.com@localhost (Christos Zoulas) wrote:

> In article <20160408090513.d1d9cd1ea02ea764e0a1b7b1%googlemail.com@localhost>,
> Sad Clouds  <cryintothebluesky%googlemail.com@localhost> wrote:
> >On Thu, 7 Apr 2016 10:48:28 -0600 (MDT)
> >Swift Griggs <swiftgriggs%gmail.com@localhost> wrote:
> >
> >> On Thu, 7 Apr 2016, Christos Zoulas wrote:
> >> > >I attached gdb on sparc64 to sshd process and after 30 seconds
> >> > >got the following
> >> > Do you have a NAT/firewall and you don't have keep state in your
> >> > pass rules?
> >> 
> >> I've also seen misconfigured NIDS system that are setup for TCP 
> >> "shootdown" (ie..  sending RSTs to both sides with valid SEQ
> >> numbers causing an instant disconnect). Occasionally they will see
> >> something in the encrypted data stream (or just the fact that it's
> >> encrypted) and shoot down the connection because it violates some
> >> network policy (usually just misconfigured to think that).
> >> 
> >> If that's the cause, it's very easy to see it in a packet trace
> >> because all the sudden out of nowhere you just see an RST hit you
> >> and kill the connection. Then on the opposite (client) side, if
> >> you take a trace at the same time, you won't see it actually
> >> _sending_ the RST. Thus, you know a NIDS spoofed it.
> >> 
> >> -Swift
> >> 
> >
> >Hello, I don't explicitly enable any NAT/Firewall rules on any of my
> >local machine. All machines are on the same LAN, connected to a
> >single 100Mbps switch. I run scp from NetBSD-7 on amd64 to NetBSD-7
> >on sparc64, sooner or later sshd on sparc64 exits with error.
> >
> >The way I manage to reproduce it:
> >
> >1. Enable tcp4csum and udp4csum for hme0 on sparc64
> >
> >2. Simulate heavy I/O on sparc64 by unpacking src.tgz which contains
> >pkgsrc, src and xsrc
> >
> >3. Start scp for a 3GB file from amd64 to sparc64
> >
> >Sooner or later sshd on sparc64 exists with error
> >
> >Disabling tcp4csum and udp4csu for hme0 and repeating the above steps
> >always succeeds to scp the entire 3GB file without any errors.
> >
> >So I'm inclined to think it's either hme0 hardware issue, or NetBSD
> >kernel bug.
> 
> Please file a PR.
> 
> christos
> 

kern/51057: hme(4) device driver bug when tcp4csum and udp4csum are
enabled