Re: bin/39233: OpenSSH fails to initialize tun(4) tunnels correctly

[Taylor R Campbell <campbell%mumble.net@localhost>]

The following reply was made to PR bin/39233; it has been noted by GNATS.

From: Taylor R Campbell <campbell%mumble.net@localhost>
To: cube%cubidou.net@localhost
Cc: gnats-bugs%NetBSD.org@localhost
Subject: Re: bin/39233: OpenSSH fails to initialize tun(4) tunnels correctly
Date: Tue, 29 Jul 2008 10:36:31 -0400

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 Sorry, that was a terrible patch.  Here's a better one (also actually
 attached this time).
 
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 Index: misc.c
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 RCS file: /cvsroot/src/crypto/dist/ssh/misc.c,v
 retrieving revision 1.21
 diff -u -r1.21 misc.c
 --- misc.c     6 Apr 2008 23:38:19 -0000       1.21
 +++ misc.c     28 Jul 2008 23:36:35 -0000
 @@ -35,6 +35,9 @@
  #include <net/if.h>
  #include <netinet/in.h>
  #include <netinet/tcp.h>
 +#ifdef __NetBSD__
 +# include <net/if_tun.h>
 +#endif
 =20
  #include <errno.h>
  #include <fcntl.h>
 @@ -636,20 +639,90 @@
        return -1;
  }
 =20
 +#if defined(__NetBSD__)
 +
 +static ssize_t
 +tun_get_device_name(int tun, int mode, char *buf, size_t buflen)
 +{
 +        if (mode =3D=3D SSH_TUNMODE_POINTOPOINT)
 +                return strlcpy(buf, "tun", buflen);
 +        else if (mode =3D=3D SSH_TUNMODE_ETHERNET)
 +                return strlcpy(buf, "tap", buflen);
 +        else
 +                return (-1);
 +}
 +
 +static int
 +tun_set_if_mode(int tun, int mode, int fd, int sock, struct ifreq *ifr)
 +{
 +      if (mode =3D=3D SSH_TUNMODE_POINTOPOINT) {
 +              int one =3D 1;
 +                /* Request the tun(4) interface to prepend four bytes
 +                   of address family to each packet delivered, which is
 +                   what OpenBSD's tun(4) expects. */
 +              return ioctl(fd, TUNSIFHEAD, &one);
 +      }
 +      return 0;
 +}
 +
 +#elif defined(__OpenBSD__) || defined(__FreeBSD__)
 +
 +static ssize_t
 +tun_get_device_name(int tun, int mode, char *buf, size_t buflen)
 +{
 +        if (mode =3D=3D SSH_TUNMODE_POINTOPOINT ||
 +            mode =3D=3D SSH_TUNMODE_ETHERNET)
 +                return strlcpy(buf, "tun", buflen);
 +        else
 +                return (-1);
 +}
 +
 +static int
 +tun_set_if_mode(int tun, int mode, int fd, int sock, struct ifreq *ifr)
 +{
 +      ifr->ifr_flags &=3D ~IFF_IP;
 +      if (mode =3D=3D SSH_TUNMODE_ETHERNET)
 +              ifr->ifr_flags |=3D IFF_LINK0;
 +      else
 +              ifr->ifr_flags &=3D ~IFF_LINK0;
 +      return ioctl(sock, SIOCSIFFLAGS, ifr);
 +}
 +
 +#else
 +
 +static ssize_t
 +tun_get_device_name(int tun, int mode, char *buf, size_t buflen)
 +{
 +        return (-1);
 +}
 +
 +static int
 +tun_set_if_mode(int tun, int mode, int fd, int sock, struct ifreq *ifr)
 +{
 +        return (-1);
 +}
 +
 +#endif
 +
  int
  tun_open(int tun, int mode)
  {
        struct ifreq ifr;
 -      char name[100];
 +      char name[100], device[100];
        int fd =3D -1, sock;
 =20
 +        if (tun_get_device_name(tun, mode, device, sizeof(device)) =3D=3D =
 -1) {
 +                debug("%s: no tunnel %d for mode %u", __func__, tun, mode);
 +              return (-1);
 +      }
 +
        /* Open the tunnel device */
        if (tun <=3D SSH_TUNID_MAX) {
 -              snprintf(name, sizeof(name), "/dev/tun%d", tun);
 +              snprintf(name, sizeof(name), "/dev/%s%d", device, tun);
                fd =3D open(name, O_RDWR);
        } else if (tun =3D=3D SSH_TUNID_ANY) {
                for (tun =3D 100; tun >=3D 0; tun--) {
 -                      snprintf(name, sizeof(name), "/dev/tun%d", tun);
 +                      snprintf(name, sizeof(name), "/dev/%s%d", device, tun);
                        if ((fd =3D open(name, O_RDWR)) >=3D 0)
                                break;
                }
 @@ -666,7 +739,7 @@
        debug("%s: %s mode %d fd %d", __func__, name, mode, fd);
 =20
        /* Set the tunnel device operation mode */
 -      snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "tun%d", tun);
 +      snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s%d", device, tun);
        if ((sock =3D socket(PF_UNIX, SOCK_STREAM, 0)) =3D=3D -1)
                goto failed;
 =20
 @@ -674,12 +747,7 @@
                goto failed;
 =20
        /* Set interface mode */
 -      ifr.ifr_flags &=3D ~IFF_UP;
 -      if (mode =3D=3D SSH_TUNMODE_ETHERNET)
 -              ifr.ifr_flags |=3D IFF_LINK0;
 -      else
 -              ifr.ifr_flags &=3D ~IFF_LINK0;
 -      if (ioctl(sock, SIOCSIFFLAGS, &ifr) =3D=3D -1)
 +      if (tun_set_if_mode(tun, mode, fd, sock, &ifr) =3D=3D -1)
                goto failed;
 =20
        /* Bring interface up */
 
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