iproute: force rtm_dst_len to 32/128

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. Print a warning to stderr to notify users.

Bug-Debian: https://bugs.debian.org/944730
Reported-By: Clément 'wxcafé' Hertling <wxcafe@wxcafe.net>
Signed-off-by: Luca Boccassi <bluca@debian.org>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

diff --git a/ip/iproute.c b/ip/iproute.c
index ebb5f160fc4437b9e0f15af3a307425b0f701483..8d4d2ff87409b76123da6e7cb1b351c7985e5411 100644 (file)
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -2069,7 +2069,18 @@ 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 && addr.bitlen != 32) {
+                               fprintf(stderr,
+                                       "Warning: /%u as prefix is invalid, only /32 (or none) is supported.\n",
+                                       addr.bitlen);
+                               req.r.rtm_dst_len = 32;
+                       } else if (req.r.rtm_family == AF_INET6 && addr.bitlen != 128) {
+                               fprintf(stderr,
+                                       "Warning: /%u as prefix is invalid, only /128 (or none) is supported.\n",
+                                       addr.bitlen);
+                               req.r.rtm_dst_len = 128;
+                       } else
+                               req.r.rtm_dst_len = addr.bitlen;
                        address_found = true;
                }
                argc--; argv++;