[libvirt] [PATCH] util: improve virNetDevTapGetRealDeviceName

[Roman Bogorodskiy]

  Michal Privoznik wrote:

> On 04/08/2018 05:40 PM, Roman Bogorodskiy wrote:
> > virNetDevTapGetRealDeviceName() is used on FreeBSD because interface
> > names (such as one sees in output of tools like ifconfig(8)) might not
> > match their /dev entity names, and for bhyve we need the latter.
> > 
> > Current implementation is not very efficient because in order to find
> > /dev name, it goes through all /dev/tap* entries and tries to issue
> > TAPGIFNAME ioctl on it. Not only this is slow, but also there's a bug in
> > this implementation when more than one NIC is passed to a VM: once we
> > find the tap interface we're looking for, we set its state to UP because
> > opening it for issuing ioctl sets it DOWN, even if it was UP before.
> > When we have more than 1 NIC for a VM, we have only last one UP because
> > others remain DOWN after unsuccessful attempts to match interface name.
> > 
> > New implementation just uses sysctl(3), so it should be faster and
> > won't make interfaces go down to get name.
> > ---
> >  src/util/virnetdevtap.c | 71 +++++++++++++++++++++----------------------------
> >  1 file changed, 30 insertions(+), 41 deletions(-)
> 
> ACK with this squashed in:
> 
> diff --git i/src/util/virnetdevtap.c w/src/util/virnetdevtap.c
> index afe4f0b3c1..bd0710ad2e 100644
> --- i/src/util/virnetdevtap.c
> +++ w/src/util/virnetdevtap.c
> @@ -40,7 +40,6 @@
>  #include <string.h>
>  #include <unistd.h>
>  #include <regex.h>
> -#include <dirent.h>
>  #include <sys/types.h>
>  #include <sys/ioctl.h>
>  #include <net/if.h>
> @@ -129,13 +128,14 @@ virNetDevTapGetRealDeviceName(char *ifname ATTRIBUTE_UNUSED)
>          return NULL;
>      }
>  
> -    ret = malloc(len);
> +    if (VIR_ALLOC_N(ret, len) < 0)
> +        return NULL;
>  
>      if (sysctl(name, 6, ret, &len, 0, 0) < 0) {
>          virReportSystemError(errno,
>                               _("Unable to get driver name for '%s'"),
>                               ifname);
> -        free(ret);
> +        VIR_FREE(ret);
>          return NULL;
>      }
>  
> 
> 
> Michal

Pushed, thanks!

Roman Bogorodskiy
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