netdev - [RFC iproute2 v2] ip route: get: allow zero-length subnet mask

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Date:   Thu, 14 Feb 2019 23:29:18 +0000
From:   Luca Boccassi <bluca@...ian.org>
To:     netdev@...r.kernel.org
Cc:     stephen@...workplumber.org, Luca Boccassi <bluca@...ian.org>,
        Clément Hertling <wxcafe@...afe.net>
Subject: [RFC iproute2 v2] ip route: get: allow zero-length subnet mask

A /0 subnet mask is theoretically valid, but ip route get doesn't allow
it:

$ ip route get 1.0.0.0/0
need at least a destination address

Change the check and remember whether we found an address or not, since
according to the documentation it's a mandatory parameter.

$ ip/ip route get 1.0.0.0/0
1.0.0.0 via 192.168.1.1 dev eth0 src 192.168.1.91 uid 1000
    cache

Reported-by: Clément Hertling <wxcafe@...afe.net>
Signed-off-by: Luca Boccassi <bluca@...ian.org>
---
v2: changed the check instead of removing it, so that "ip route get"
fails since the address is a mandatory parameter according to the
manpage.

 ip/iproute.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/ip/iproute.c b/ip/iproute.c
index 5f58a3b3..cc02a3e1 100644
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -1932,6 +1932,7 @@ static int iproute_get(int argc, char **argv)
 	int fib_match = 0;
 	int from_ok = 0;
 	unsigned int mark = 0;
+	bool address_found = false;
 
 	iproute_reset_filter(0);
 	filter.cloned = 2;
@@ -2037,11 +2038,12 @@ static int iproute_get(int argc, char **argv)
 				addattr_l(&req.n, sizeof(req),
 					  RTA_DST, &addr.data, addr.bytelen);
 			req.r.rtm_dst_len = addr.bitlen;
+			address_found = true;
 		}
 		argc--; argv++;
 	}
 
-	if (req.r.rtm_dst_len == 0) {
+	if (!address_found) {
 		fprintf(stderr, "need at least a destination address\n");
 		return -1;
 	}
-- 
2.20.1