[ovs-dev] [PATCH v2] socket-util: Support sendmmsg() regardless of platform.

[Ben Pfaff]

Thanks.  I applied this to master.

On Thu, Jul 13, 2017 at 10:46:44AM +0800, Gao Zhenyu wrote:
> LGTM.
> 
> Thanks
> Zhenyu Gao
> 
> 2017-07-13 8:39 GMT+08:00 Ben Pfaff <blp at ovn.org>:
> 
> > This will have its first user in an upcoming commit.
> >
> > Signed-off-by: Ben Pfaff <blp at ovn.org>
> > ---
> > v1->v2: Note that FreeBSD also has sendmmsg.  Fix sendmsg() return type.
> >
> >  configure.ac                |  3 ++-
> >  include/sparse/sys/socket.h |  5 +++++
> >  lib/socket-util.c           | 38 ++++++++++++++++++++++++++++++++++++++
> >  lib/socket-util.h           | 27 +++++++++++++++++++++++++++
> >  4 files changed, 72 insertions(+), 1 deletion(-)
> >
> > diff --git a/configure.ac b/configure.ac
> > index 6404b5fc1222..9ef6aad3a36e 100644
> > --- a/configure.ac
> > +++ b/configure.ac
> > @@ -106,7 +106,8 @@ AC_CHECK_DECLS([sys_siglist], [], [], [[#include
> > <signal.h>]])
> >  AC_CHECK_MEMBERS([struct stat.st_mtim.tv_nsec, struct stat.st_mtimensec],
> >    [], [], [[#include <sys/stat.h>]])
> >  AC_CHECK_MEMBERS([struct ifreq.ifr_flagshigh], [], [], [[#include
> > <net/if.h>]])
> > -AC_CHECK_FUNCS([mlockall strnlen getloadavg statvfs getmntent_r])
> > +AC_CHECK_MEMBERS([struct mmsghdr.msg_len], [], [], [[#include
> > <sys/socket.h>]])
> > +AC_CHECK_FUNCS([mlockall strnlen getloadavg statvfs getmntent_r sendmmsg])
> >  AC_CHECK_HEADERS([mntent.h sys/statvfs.h linux/types.h linux/if_ether.h
> > stdatomic.h])
> >  AC_CHECK_HEADERS([net/if_mib.h], [], [], [[#include <sys/types.h>
> >  #include <net/if.h>]])
> > diff --git a/include/sparse/sys/socket.h b/include/sparse/sys/socket.h
> > index 3212bf4b7f13..88a5387e7f9b 100644
> > --- a/include/sparse/sys/socket.h
> > +++ b/include/sparse/sys/socket.h
> > @@ -75,6 +75,11 @@ __cmsg_nxthdr(struct msghdr *msg, struct cmsghdr *cmsg)
> >              : NULL);
> >  }
> >
> > +struct mmsghdr {
> > +    struct msghdr msg_hdr;
> > +    unsigned int msg_len;
> > +};
> > +
> >  enum {
> >      SCM_RIGHTS = 1
> >  };
> > diff --git a/lib/socket-util.c b/lib/socket-util.c
> > index 2c0f1e62bd99..7148ae3da67c 100644
> > --- a/lib/socket-util.c
> > +++ b/lib/socket-util.c
> > @@ -1020,3 +1020,41 @@ sock_strerror(int error)
> >      return ovs_strerror(error);
> >  #endif
> >  }
> > +
> > +static int
> > +emulate_sendmmsg(int fd, struct mmsghdr *msgs, unsigned int n,
> > +                 unsigned int flags)
> > +{
> > +    for (unsigned int i = 0; i < n; i++) {
> > +        ssize_t retval = sendmsg(fd, &msgs[i].msg_hdr, flags);
> > +        if (retval < 0) {
> > +            return i ? i : retval;
> > +        }
> > +        msgs[i].msg_len = retval;
> > +    }
> > +    return n;
> > +}
> > +
> > +#ifndef HAVE_SENDMMSG
> > +int
> > +sendmmsg(int fd, struct mmsghdr *msgs, unsigned int n, unsigned int flags)
> > +{
> > +    return emulate_sendmmsg(fd, msgs, n, flags);
> > +}
> > +#else
> > +int
> > +wrap_sendmmsg(int fd, struct mmsghdr *msgs, unsigned int n, unsigned int
> > flags)
> > +{
> > +    static bool sendmmsg_broken = false;
> > +    if (!sendmmsg_broken) {
> > +        int save_errno = errno;
> > +        int retval = sendmmsg(fd, msgs, n, flags);
> > +        if (retval >= 0 || errno != ENOSYS) {
> > +            return retval;
> > +        }
> > +        sendmmsg_broken = true;
> > +        errno = save_errno;
> > +    }
> > +    return emulate_sendmmsg(fd, msgs, n, flags);
> > +}
> > +#endif
> > diff --git a/lib/socket-util.h b/lib/socket-util.h
> > index 5bf76a40eb84..ef316cb8cc72 100644
> > --- a/lib/socket-util.h
> > +++ b/lib/socket-util.h
> > @@ -87,6 +87,33 @@ int make_unix_socket(int style, bool nonblock,
> >                       const char *bind_path, const char *connect_path);
> >  int get_unix_name_len(const struct sockaddr_un *sun, socklen_t sun_len);
> >
> > +/* Universal sendmmsg support.
> > + *
> > + * Some platforms, such as new enough Linux and FreeBSD, support
> > sendmmsg, but
> > + * other platforms (or older ones) do not.  We add the following
> > infrastructure
> > + * to allow all code to use sendmmsg, regardless of platform support:
> > + *
> > + *   - For platforms that lack sendmmsg entirely, we emulate it.
> > + *
> > + *   - Some platforms have sendmmsg() in the C library but not in the
> > kernel.
> > + *     For example, this is true if a Linux system has a newer glibc with
> > an
> > + *     old kernel.  To compensate, even if sendmmsg() appears to be
> > available,
> > + *     we still wrap it with a handler that uses our emulation if
> > sendmmsg()
> > + *     returns ENOSYS.
> > + */
> > +#ifndef HAVE_STRUCT_MMSGHDR_MSG_LEN
> > +struct mmsghdr {
> > +    struct msghdr msg_hdr;
> > +    unsigned int msg_len;
> > +};
> > +#endif
> > +#ifndef HAVE_SENDMMSG
> > +int sendmmsg(int, struct mmsghdr *, unsigned int, unsigned int);
> > +#else
> > +#define sendmmsg wrap_sendmmsg
> > +int wrap_sendmmsg(int, struct mmsghdr *, unsigned int, unsigned int);
> > +#endif
> > +
> >  /* Helpers for calling ioctl() on an AF_INET socket. */
> >  struct ifreq;
> >  int af_inet_ioctl(unsigned long int command, const void *arg);
> > --
> > 2.10.2
> >
> > _______________________________________________
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> > dev at openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev
> >