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From: orc <orc@sibserver.ru>
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Subject: Re: openssh and sendmsg() problem
Date: Wed, 27 Jun 2012 03:39:34 +0800
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On Tue, 26 Jun 2012 15:08:23 -0400
Rich Felker <dalias@aerifal.cx> wrote:

> On Wed, Jun 27, 2012 at 02:16:40AM +0800, orc wrote:
> > On Tue, 26 Jun 2012 13:32:05 -0400
> > Rich Felker <dalias@aerifal.cx> wrote:
> > 
> > > On Wed, Jun 27, 2012 at 01:24:41AM +0800, orc wrote:
> > > > On Tue, 26 Jun 2012 12:01:06 -0400
> > > > Rich Felker <dalias@aerifal.cx> wrote:
> > > > 
> > > > > On Tue, Jun 26, 2012 at 02:00:17PM +0200, Szabolcs Nagy wrote:
> > > > > > * orc <orc@sibserver.ru> [2012-06-26 19:01:46 +0800]:
> > > > > > > strace shows that sendmsg system call returns EINVAL:
> > > > > > > 
> > > > > > > sendmsg(5, {msg_name(0)=NULL, msg_iov(1)=[{"\0", 1}],
> > > > > > > msg_controllen=24, {cmsg_len=20, cmsg_level=SOL_SOCKET,
> > > > > > > cmsg_ type=SCM_RIGHTS, {4, 385875968}}, msg_flags=0}, 0)
> > > > > > > = -1 EINVAL (Invalid argument)
> > > > > > > 
> > 
> > strace from glibc system on this syscall:
> > 
> > sendmsg(5, {msg_name(0)=NULL, msg_iov(1)=[{"\0", 1}],
> > msg_controllen=24, {cmsg_len=20, cmsg_level=SOL_SOCKET,
> > cmsg_type=SCM_RIGHTS, {4}}, msg_flags=0}, 0) = 1 sendmsg(5,
> > {msg_name(0)=NULL, msg_iov(1)=[{"\0", 1}], msg_controllen=24,
> > {cmsg_len=20, cmsg_level=SOL_SOCKET, cmsg_type=SCM_RIGHTS, {6}},
> > msg_flags=0}, 0) = 1
> 
> I don't quite understand this from the strace, but it looks like
> there's an issue with the size of cmsg structures on 64-bit machines
> due to another buggy kernel socklen_t/size_t mismatch. I'm not sure
> how it can be worked around, but musl's failure to work around it is a
> flaw that needs to be fixed. glibc just violates POSIX and defines
> the wrong type.
> 
> Rich

And kernel too.

Both they define incompatible msghdr and cmsghdr structs.
The problem sits in cmsghdr struct, changing it's first member type to
'size_t' solves openssh issue.