On Fri, 17 May 2019 10:59:13 -0700
David Ahern <dsah...@kernel.org> wrote:
> From: David Ahern <dsah...@gmail.com>
>
> Jason reported that ip route get with a prefix length is now
> failing:
> $ 192.168.50.0/24
> RTNETLINK answers: Invalid argument
>
> iproute2 now uses strict mode and strict mode in the kernel
> requires rtm_dst_len to be 32. Non-strict mode ignores the
> prefix length, so this allows ip to work without affecting
> existing users who add a prefix length to the request.
>
> Fixes: aea41afcfd6d6 ("ip bridge: Set NETLINK_GET_STRICT_CHK on socket")
> Reported-by: Jason A. Donenfeld <ja...@zx2c4.com>
> Signed-off-by: David Ahern <dsah...@gmail.com>
> ---
> ip/iproute.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/ip/iproute.c b/ip/iproute.c
> index 2b3dcc5dbd53..d980b86ffd42 100644
> --- a/ip/iproute.c
> +++ b/ip/iproute.c
> @@ -2035,7 +2035,11 @@ static int iproute_get(int argc, char **argv)
> if (addr.bytelen)
> addattr_l(&req.n, sizeof(req),
> RTA_DST, &addr.data, addr.bytelen);
> - req.r.rtm_dst_len = addr.bitlen;
> + /* kernel ignores prefix length on 'route get'
> + * requests; to allow ip to work with strict mode
> + * but not break existing users, just set to 32
> + */
> + req.r.rtm_dst_len = 32;
> address_found = true;
> }
> argc--; argv++;
I don't like silently ignoring things. It was wrong before and it
is trapped now.
Probably better to error out in iproute2 if any prefix is given.
