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Date: Fri, 1 Apr 2016 13:31:46 +0200
From: Szabolcs Nagy <>
Subject: Re: recvmsg/sendmsg broken on mips64

* Sebastian Gottschall <> [2016-04-01 12:29:35 +0200]:

> Am 01.04.2016 um 11:49 schrieb Szabolcs Nagy:
> >* Sebastian Gottschall <> [2016-04-01 11:16:20 +0200]:
> >>I discovered that the whole recvmsg/sendmsg code is broken in mips64
> >>but i found also the solution
> >>i throwed out all the _pad1, _pad2 crap in socket.h and the corrosponding
> >>code in recvmsg.c etc.
> >>and used size_t instead. this works at the end. i see no reason for this
> >>padding, since using the correct datatype will handle it in the same way.
> >>this solution may also work for other 64 bit targets. so proposal is fixing
> >>the datatype instead of using int with padding in case of 64 bit
> >>
> >the padding is needed, i think __BIG_ENDIAN
> >or __LITTLE_ENDIAN might not be defined properly.
> i checked this already. it was defined properly. the only solution was using
> the correct datatypes as defined in the kernel and i also checked uclibc. it
> uses also just size_t and nothing else.
> the padding results in the same datatype size, just clears the upper and
> lower word. but this doesnt seem to be neccessary
> >your fix is non-conforming and breaks both abi and api,
> >the definition must match
> socklen_t would result in the same 64bit datatype instead of int + pad
> (which is 64 bit too). so its conforming.
> i mached by header variant by reading the kernel headers which uses size_t
> instead of socketlen_t
> so i assume socketlen_t maches size_t

msg_iovlen must be int
msg_controllen and cmsg_len must be socklen_t

the socklen_t typedef must match what the size
the socket syscalls expect which is int.

uclibc and linux uapi is known to be broken,
linux uapi is not fixed because of abi compat
but we can work this around in musl.

if the endian macros are defined then the padding
should work.

> >
> >
> >
> >>this here is my working struct in mips64 (big endian)
> >>
> >>struct msghdr {
> >>         void *msg_name;
> >>         socklen_t msg_namelen;
> >>         struct iovec *msg_iov;
> >>         size_t msg_iovlen;
> >>         void *msg_control;
> >>         size_t msg_controllen;
> >>         int msg_flags;
> >>};
> >>
> >>struct cmsghdr {
> >>         size_t cmsg_len;
> >>         int cmsg_level;
> >>         int cmsg_type;
> >>};
> >>
> >>
> >>Sebastian

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