Re: [PATCH] Linux: Implement opensock using Netlink sockets

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

On 18/06/2018 07:50, Florian Weimer wrote:
> inet/tst-inet6_scopeid_pton uses __opensock indirectly, to call ioctl
> with SIOCGIFINDEX, and it still works after this change.
> 
> 2018-06-18  Florian Weimer  <fweimer@redhat.com>
> 
> 	* sysdeps/unix/sysv/linux/opensock.c (__opensock): Unconditionally
> 	return a Netlink socket.
> 	* sysdeps/unix/sysv/linux/s390/opensock.c: Remove file.

Similar to a previous attempt to use AF_NETLINK sockets as default [1],
I am seeing some regression on testcases with Linux 4.4.0-116-generic:

FAIL: inet/bug-if1
FAIL: inet/test_ifindex
FAIL: inet/tst-inet6_scopeid_pton

$ ./testrun.sh inet/bug-if1
errno = 95 (Operation not supported), expected 6 (No such device or address)

$ strace -f ./testrun.sh inet/bug-if1 --direct
[...]
socket(AF_NETLINK, SOCK_DGRAM|SOCK_CLOEXEC, NETLINK_ROUTE) = 3
ioctl(3, SIOCGIFNAME, {ifr_index=0})    = -1 EOPNOTSUPP (Operation not supported)
[...]


$ ./testrun.sh inet/test_ifindex
Idx            Name | Idx           Name
  1              lo |   0         (null)      fail
  2            eth0 |   0         (null)      fail
  3          virbr0 |   0         (null)      fail
  4      virbr0-nic |   0         (null)      fail
  5          lxcbr0 |   0         (null)      fail
  6         docker0 |   0         (null)      fail

$ strace -f ./testrun.sh inet/test_ifindex --direct
[...]
socket(AF_NETLINK, SOCK_DGRAM|SOCK_CLOEXEC, NETLINK_ROUTE) = 3
ioctl(3, SIOCGIFINDEX, {ifr_name="lxcbr0"}) = -1 EOPNOTSUPP (Operation not supported)
[...]


$ ./testrun.sh inet/tst-inet6_scopeid_pton
error: unexpected failure for fe80::1%lo
error: unexpected result for for fe80::1%lo
  expected: 1
  actual:   2
error: unexpected getaddrinfo failure for fe80::1%lo (AF_UNSPEC)
error: unexpected getaddrinfo failure for fe80::1%lo (AF_INET6)
error: unexpected failure for ff02::1%lo
error: unexpected result for for ff02::1%lo
  expected: 1
  actual:   2
error: unexpected getaddrinfo failure for ff02::1%lo (AF_UNSPEC)
error: unexpected getaddrinfo failure for ff02::1%lo (AF_INET6)
error: unexpected failure for ff01::1%lo
error: unexpected result for for ff01::1%lo
  expected: 1
  actual:   2
error: unexpected getaddrinfo failure for ff01::1%lo (AF_UNSPEC)
error: unexpected getaddrinfo failure for ff01::1%lo (AF_INET6)
error: 12 test failures

$ strace -f ./testrun.sh inet/tst-inet6_scopeid_pton --direct
[...]
socket(AF_NETLINK, SOCK_DGRAM|SOCK_CLOEXEC, NETLINK_ROUTE) = 3
ioctl(3, SIOCGIFINDEX, {ifr_name="lo"}) = -1 EOPNOTSUPP (Operation not supported)
[...]

[1] https://sourceware.org/ml/libc-alpha/2017-08/msg01091.html

> 
> diff --git a/sysdeps/unix/sysv/linux/opensock.c b/sysdeps/unix/sysv/linux/opensock.c
> index fd9445bc3b..f5d7322c35 100644
> --- a/sysdeps/unix/sysv/linux/opensock.c
> +++ b/sysdeps/unix/sysv/linux/opensock.c
> @@ -15,100 +15,15 @@
>     License along with the GNU C Library; if not, see
>     <http://www.gnu.org/licenses/>.  */
>  
> -#include <assert.h>
> -#include <errno.h>
> -#include <stdio.h>
> -#include <string.h>
> -#include <unistd.h>
>  #include <sys/socket.h>
> +#include <linux/netlink.h>
>  
>  /* Return a socket of any type.  The socket can be used in subsequent
>     ioctl calls to talk to the kernel.  */
>  int
>  __opensock (void)
>  {
> -  static int last_family;	/* Available socket family we will use.  */
> -  static int last_type;
> -  static const struct
> -  {
> -    int family;
> -    const char procname[15];
> -  } afs[] =
> -    {
> -      { AF_UNIX, "net/unix" },
> -      { AF_INET, "" },
> -      { AF_INET6, "net/if_inet6" },
> -      { AF_AX25, "net/ax25" },
> -      { AF_NETROM, "net/nr" },
> -      { AF_ROSE, "net/rose" },
> -      { AF_IPX, "net/ipx" },
> -      { AF_APPLETALK, "net/appletalk" },
> -      { AF_ECONET, "sys/net/econet" },
> -      { AF_ASH, "sys/net/ash" },
> -      { AF_X25, "net/x25" },
> -#ifdef NEED_AF_IUCV
> -      { AF_IUCV, "net/iucv" }
> -#endif
> -    };
> -#define nafs (sizeof (afs) / sizeof (afs[0]))
> -  char fname[sizeof "/proc/" + 14];
> -  int result;
> -  int has_proc;
> -  size_t cnt;
> -
> -  /* We already know which family to use from the last call.  Use it
> -     again.  */
> -  if (last_family != 0)
> -    {
> -      assert (last_type != 0);
> -
> -      result = __socket (last_family, last_type | SOCK_CLOEXEC, 0);
> -      if (result != -1 || errno != EAFNOSUPPORT)
> -	/* Maybe the socket type isn't supported anymore (module is
> -	   unloaded).  In this case again try to find the type.  */
> -	return result;
> -
> -      /* Reset the values.  They seem not valid anymore.  */
> -      last_family = 0;
> -      last_type = 0;
> -    }
> -
> -  /* Check whether the /proc filesystem is available.  */
> -  has_proc = __access ("/proc/net", R_OK) != -1;
> -  strcpy (fname, "/proc/");
> -
> -  /* Iterate over the interface families and find one which is
> -     available.  */
> -  for (cnt = 0; cnt < nafs; ++cnt)
> -    {
> -      int type = SOCK_DGRAM;
> -
> -      if (has_proc && afs[cnt].procname[0] != '\0')
> -	{
> -	  strcpy (fname + 6, afs[cnt].procname);
> -	  if (__access (fname, R_OK) == -1)
> -	    /* The /proc entry is not available.  I.e., we cannot
> -	       create a socket of this type (without loading the
> -	       module).  Don't look for it since this might trigger
> -	       loading the module.  */
> -	    continue;
> -	}
> -
> -      if (afs[cnt].family == AF_NETROM || afs[cnt].family == AF_X25)
> -	type = SOCK_SEQPACKET;
> -
> -      result = __socket (afs[cnt].family, type | SOCK_CLOEXEC, 0);
> -      if (result != -1)
> -	{
> -	  /* Found an available family.  */
> -	  last_type = type;
> -	  last_family = afs[cnt].family;
> -	  return result;
> -	}
> -    }
> -
> -  /* None of the protocol families is available.  It is unclear what kind
> -     of error is returned.  ENOENT seems like a reasonable choice.  */
> -  __set_errno (ENOENT);
> -  return -1;
> +  /* Netlink support is always part of the kernel, so we just use a
> +     netlink socket.  */
> +  return __socket (PF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
>  }
> diff --git a/sysdeps/unix/sysv/linux/s390/opensock.c b/sysdeps/unix/sysv/linux/s390/opensock.c
> deleted file mode 100644
> index f099d651ff..0000000000
> --- a/sysdeps/unix/sysv/linux/s390/opensock.c
> +++ /dev/null
> @@ -1,2 +0,0 @@
> -#define NEED_AF_IUCV 1
> -#include "../opensock.c"
>