Where fd is a socket (datagram or raw) with IPv6 protocol family,
getsockopt(fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, ...) succeeds, but
the returned hop limit is -1. connect()'ing the socket first does
not solve the problem.
An IPv6 socket's hoplimit value is not set at creation time, instead,
the hoplimit in an outgoing packet is set dynamically at transmit
time to one of the following (in this order):
1. Hoplimit route metric (if set)
2. Outgoing interface value (/proc/sys/net/ipv6/conf/ethX/hop_limit)
3. Global IPv6 value (/proc/sys/net/ipv6/conf/all/hop_limit)
A setsockopt() value *will* override this.
Relevant standard (RFC 3493) notes:
The IPV6_UNICAST_HOPS option may be used with getsockopt() to
determine the hop limit value that the system will use for subsequent
unicast packets sent via that socket.
I don't reckon -1 could be the hop limit value.
-1 means un-initialized.
IMHO, the value from
case 1 (if socket is connected to some destination), otherwise case 2
(if bound to a scope interface) or ultimately the default hop limit
ought to be returned instead, as it will be most often correct, while
the current behavior is always wrong, unless setsockopt() has been used
first. I don't if some people may think doing a route lookup in
getsockopt might be overly expensive, but at least the two other cases
should be ok, particularly the last one.
The following patch seems to work for me, but this code has behaved this
way for a while, so don't know if it will break any existing apps.
-Brian
Signed-off-by: Brian Haley <[EMAIL PROTECTED]>
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 1eafcfc..352690e 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -978,12 +978,27 @@ static int do_ipv6_getsockopt(struct soc
break;
case IPV6_UNICAST_HOPS:
- val = np->hop_limit;
- break;
-
case IPV6_MULTICAST_HOPS:
- val = np->mcast_hops;
+ {
+ struct dst_entry *dst;
+
+ if (optname == IPV6_UNICAST_HOPS)
+ val = np->hop_limit;
+ else
+ val = np->mcast_hops;
+
+ dst = sk_dst_get(sk);
+ if (dst) {
+ if (val < 0)
+ val = dst_metric(dst, RTAX_HOPLIMIT);
+ if (val < 0)
+ val = ipv6_get_hoplimit(dst->dev);
+ dst_release(dst);
+ }
+ if (val < 0)
+ val = ipv6_devconf.hop_limit;
break;
+ }
case IPV6_MULTICAST_LOOP:
val = np->mc_loop;
