tap-bsd: use user-specified tap device if it already exists

Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Ed Maste <emaste@freebsd.org>
---
As an aside this was reviewed on FreeBSD's Phabricator here:
https://reviews.freebsd.org/D3969

Resend with Signed-off-by.

 net/tap-bsd.c | 38 +++++++++++++++++++++++++++++++++-----
 1 file changed, 33 insertions(+), 5 deletions(-)

Ccing the maintainers.

El 23/10/15 a les 17.53, Ed Maste ha escrit:
> Acked-by: Roger Pau Monné <roger.pau@citrix.com>
> Signed-off-by: Ed Maste <emaste@freebsd.org>
> ---
> As an aside this was reviewed on FreeBSD's Phabricator here:
> https://reviews.freebsd.org/D3969
> 
> Resend with Signed-off-by.
> 
>  net/tap-bsd.c | 38 +++++++++++++++++++++++++++++++++-----
>  1 file changed, 33 insertions(+), 5 deletions(-)
> 
> diff --git a/net/tap-bsd.c b/net/tap-bsd.c
> index 7028d9b..0103a97 100644
> --- a/net/tap-bsd.c
> +++ b/net/tap-bsd.c
> @@ -109,8 +109,7 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
>  
>  #define PATH_NET_TAP "/dev/tap"
>  
> -int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
> -             int vnet_hdr_required, int mq_required, Error **errp)
> +static int tap_open_clone(char *ifname, int ifname_size, Error **errp)
>  {
>      int fd, s, ret;
>      struct ifreq ifr;
> @@ -126,7 +125,8 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
>      ret = ioctl(fd, TAPGIFNAME, (void *)&ifr);
>      if (ret < 0) {
>          error_setg_errno(errp, errno, "could not get tap interface name");
> -        goto error;
> +        close(fd);
> +        return -1;
>      }
>  
>      if (ifname[0] != '\0') {
> @@ -135,19 +135,47 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
>          if (s < 0) {
>              error_setg_errno(errp, errno,
>                               "could not open socket to set interface name");
> -            goto error;
> +            close(fd);
> +            return -1;
>          }
>          ifr.ifr_data = ifname;
>          ret = ioctl(s, SIOCSIFNAME, (void *)&ifr);
>          close(s);
>          if (ret < 0) {
>              error_setg(errp, "could not set tap interface name");
> -            goto error;
> +            close(fd);
> +            return -1;
>          }
>      } else {
>          pstrcpy(ifname, ifname_size, ifr.ifr_name);
>      }
>  
> +    return fd;
> +}
> +
> +int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
> +             int vnet_hdr_required, int mq_required, Error **errp)
> +{
> +    int fd = -1;
> +
> +    /* If the specified tap device already exists just use it. */
> +    if (ifname[0] != '\0') {
> +        char dname[100];
> +        snprintf(dname, sizeof dname, "/dev/%s", ifname);
> +        TFR(fd = open(dname, O_RDWR));
> +        if (fd < 0 && errno != ENOENT) {
> +            error_setg_errno(errp, errno, "could not open %s", dname);
> +            return -1;
> +        }
> +    }
> +
> +    if (fd < 0) {
> +        /* Tap device not specified or does not exist. */
> +        if ((fd = tap_open_clone(ifname, ifname_size, errp)) < 0) {
> +            return -1;
> +        }
> +    }
> +
>      if (*vnet_hdr) {
>          /* BSD doesn't have IFF_VNET_HDR */
>          *vnet_hdr = 0;
>

Applied to -trivial, thank you!

/mjt