[PATCH iproute2] iproute get: force rtm_dst_len to 32/128

[Luca Boccassi <bluca@debian.org>]

Since NETLINK_GET_STRICT_CHK was enabled, the kernel rejects commands
that pass a prefix length, eg:

 ip route get `1.0.0.0/1
  Error: ipv4: Invalid values in header for route get request.
 ip route get 0.0.0.0/0
  Error: ipv4: rtm_src_len and rtm_dst_len must be 32 for IPv4

Since there's no point in setting a rtm_dst_len that we know is going
to be rejected, just force it to the right value if it's passed on
the command line.

Bug-Debian: https://bugs.debian.org/944730
Reported-By: Clément 'wxcafé' Hertling <wxcafe@wxcafe.net>
Signed-off-by: Luca Boccassi <bluca@debian.org>
---
As mentioned by David on:

https://www.spinics.net/lists/netdev/msg624125.html

 ip/iproute.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/ip/iproute.c b/ip/iproute.c
index ebb5f160..3646d531 100644
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -2069,7 +2069,12 @@ 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;
+			if (req.r.rtm_family == AF_INET)
+				req.r.rtm_dst_len = 32;
+			else if (req.r.rtm_family == AF_INET6)
+				req.r.rtm_dst_len = 128;
+			else
+				req.r.rtm_dst_len = addr.bitlen;
 			address_found = true;
 		}
 		argc--; argv++;
-- 
2.29.2