[PATCH iproute2] ip tap: Simplify add 'tap' device w/o mode

[PATCH iproute2] ip tap: Simplify add 'tap' device w/o mode

[Vadim Kochan]

From: Vadim Kochan <vadim4j@gmail.com>

It allows add 'tap' device w/o specify mode:

    # ip tap add tap0

instead of return error message.

Signed-off-by: Vadim Kochan <vadim4j@gmail.com>
---
 ip/iptuntap.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/ip/iptuntap.c b/ip/iptuntap.c
index b9b28a1..61b6c19 100644
--- a/ip/iptuntap.c
+++ b/ip/iptuntap.c
@@ -107,6 +107,7 @@ static int tap_del_ioctl(struct ifreq *ifr)
 static int parse_args(int argc, char **argv, struct ifreq *ifr, uid_t *uid, gid_t *gid)
 {
 	int count = 0;
+	char *cmd = *(argv - 2);
 
 	memset(ifr, 0, sizeof(*ifr));
 
@@ -187,8 +188,12 @@ static int parse_args(int argc, char **argv, struct ifreq *ifr, uid_t *uid, gid_
 	}
 
 	if (!(ifr->ifr_flags & TUN_TYPE_MASK)) {
-		fprintf(stderr, "You failed to specify a tunnel mode\n");
-		return -1;
+		if(strncmp("tap", cmd, 3) == 0) {
+			ifr->ifr_flags |= IFF_TAP;
+		} else {
+			fprintf(stderr, "You failed to specify a tunnel mode\n");
+			return -1;
+		}
 	}
 
 	return 0;
-- 
2.2.2

Re: [PATCH iproute2] ip tap: Simplify add 'tap' device w/o mode

[Stephen Hemminger]

On Sat, 28 Feb 2015 11:59:46 +0200
Vadim Kochan <vadim4j@gmail.com> wrote:

> From: Vadim Kochan <vadim4j@gmail.com>
> 
> It allows add 'tap' device w/o specify mode:
> 
>     # ip tap add tap0
> 
> instead of return error message.
> 
> Signed-off-by: Vadim Kochan <vadim4j@gmail.com>

No. mode should not depend on device name.

Also, I noticed that reading kernel code it is possible to
create a broken tun device if type is not set.

Re: [PATCH iproute2] ip tap: Simplify add 'tap' device w/o mode

[Jonathon Reinhart]

On Sun, Mar 1, 2015 at 5:07 PM, Stephen Hemminger
<stephen@networkplumber.org> wrote:
> No. mode should not depend on device name.

Isn't this looking at the "tap" part of "ip tap", not the device name?

Re: [PATCH iproute2] ip tap: Simplify add 'tap' device w/o mode

[Vadim Kochan]

On Sun, Mar 01, 2015 at 05:13:39PM -0500, Jonathon Reinhart wrote:
> On Sun, Mar 1, 2015 at 5:07 PM, Stephen Hemminger
> <stephen@networkplumber.org> wrote:
> > No. mode should not depend on device name.
> 
> Isn't this looking at the "tap" part of "ip tap", not the device name?

Right it checks 'ip tap' not the device name.

Re: [PATCH iproute2] ip tap: Simplify add 'tap' device w/o mode

[Vadim Kochan]

On Sun, Mar 01, 2015 at 02:07:15PM -0800, Stephen Hemminger wrote:
> On Sat, 28 Feb 2015 11:59:46 +0200
> Vadim Kochan <vadim4j@gmail.com> wrote:
> 
> > From: Vadim Kochan <vadim4j@gmail.com>
> > 
> > It allows add 'tap' device w/o specify mode:
> > 
> >     # ip tap add tap0
> > 
> > instead of return error message.
> > 
> > Signed-off-by: Vadim Kochan <vadim4j@gmail.com>
> 
> No. mode should not depend on device name.
> 
> Also, I noticed that reading kernel code it is possible to
> create a broken tun device if type is not set.
> 

Is it still bad if it checks for 'tap' in 'ip tap' ?