From: Phil Sutter <phil@nwl.cc>
Date: Tue, 24 Nov 2015 14:45:31 +0000 (+0100)
Subject: iproute: restrict hoplimit values to be in range [0; 255]
X-Git-Tag: v4.4.0~33
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ea6cbab792f7bb8813f1b24cc1f4bd4caad8ccbe;p=thirdparty%2Fiproute2.git

iproute: restrict hoplimit values to be in range [0; 255]

Technically, the range of possible hoplimit values are defined by IPv4
and IPv6 header formats. Both define the field to be eight bits in size,
which leads to a value range of [0;255]. Setting a packet's hoplimit
field to 0 though makes not much sense, as the next hop would
immediately drop the packet. Therefore Linux uses 0 as a special value
indicating to use the system's default hoplimit (configurable via
sysctl). In iproute, setting the hoplimit of a route to 0 is equivalent
to omitting the hoplimit parameter alltogether, so it is actually not
necessary to allow that value to be specified, but keep it anyway for
backwards compatibility.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---

diff --git a/ip/iproute.c b/ip/iproute.c
index c0ef7bfe7..aed1038e5 100644
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -931,7 +931,7 @@ static int iproute_modify(int cmd, unsigned flags, int argc, char **argv)
 				mxlock |= (1<<RTAX_HOPLIMIT);
 				NEXT_ARG();
 			}
-			if (get_unsigned(&hoplimit, *argv, 0))
+			if (get_unsigned(&hoplimit, *argv, 0) || hoplimit > 255)
 				invarg("\"hoplimit\" value is invalid\n", *argv);
 			rta_addattr32(mxrta, sizeof(mxbuf), RTAX_HOPLIMIT, hoplimit);
 		} else if (strcmp(*argv, "advmss") == 0) {