Re: [PATCH] ip_gre: CONFIG_IPV6_MODULE support

[Eric Dumazet <eric.dumazet@gmail.com>]

Le mardi 28 septembre 2010 à 10:48 +0200, Eric Dumazet a écrit :
> Le mardi 28 septembre 2010 à 17:41 +0900, Herbert Xu a écrit :
> > Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > > ipv6 can be a module, we should test CONFIG_IPV6 and CONFIG_IPV6_MODULE
> > > to enable ipv6 bits in ip_gre.
> > > 
> > > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> > 
> > To do this safely, we also need to disallow IPV6=m and GRE=y.
> > 
> > Cheers,
> 

I even remember Patrick warned about this 30 months ago.... Doh...

http://www.kerneltrap.com/mailarchive/linux-netdev/2008/1/22/590393

Given its now rare ipv6 is not loaded, what about following patch ?

Thanks !

Tested here, with a non loaded ipv6 module.


[PATCH] ipv6: introduce call_icmpv6_send()

ip_gre module has a dependency against IPv6:

It needs to call icmpv6_send(), while this symbol is available only if
IPv6 module is loaded (or static)

Introduce call_icmpv6_send(), provided in core network, to indirectly
call icmpv6_send() function if available.

Reported-by: Patrick McHardy <kaber@trash.net>
Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
 include/net/icmp.h |    6 ++++++
 net/ipv4/icmp.c    |   33 +++++++++++++++++++++++++++++++++
 net/ipv4/ip_gre.c  |    2 +-
 net/ipv6/icmp.c    |    2 ++
 4 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/include/net/icmp.h b/include/net/icmp.h
index 6e991e0..ec45a4f 100644
--- a/include/net/icmp.h
+++ b/include/net/icmp.h
@@ -48,4 +48,10 @@ extern void	icmp_out_count(struct net *net, unsigned char type);
 /* Move into dst.h ? */
 extern int 	xrlim_allow(struct dst_entry *dst, int timeout);
 
+extern int register_icmpv6_send(void (*func)(struct sk_buff *skb, u8 type,
+					     u8 code, __u32 info));
+extern int unregister_icmpv6_send(void);
+extern void call_icmpv6_send(struct sk_buff *skb, u8 type,
+			     u8 code, __u32 info);
+
 #endif	/* _ICMP_H */
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index a0d847c..4c5b817 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -1217,3 +1217,36 @@ int __init icmp_init(void)
 {
 	return register_pernet_subsys(&icmp_sk_ops);
 }
+
+
+/* wrappers to call icmpv6_send() if ipv6 module is loaded */
+
+static void __rcu (*icmpv6_send_ptr)(struct sk_buff *skb, u8 type, u8 code,
+				     __u32 info);
+
+int register_icmpv6_send(void (*func)(struct sk_buff *skb, u8 type, u8 code,
+				      __u32 info))
+{
+	rcu_assign_pointer(icmpv6_send_ptr, func);
+	return 0;
+}
+EXPORT_SYMBOL(register_icmpv6_send);
+
+int unregister_icmpv6_send(void)
+{
+	rcu_assign_pointer(icmpv6_send_ptr, NULL);
+	synchronize_rcu();
+	return 0;
+}
+EXPORT_SYMBOL(unregister_icmpv6_send);
+
+/* called with rcu_read_lock */
+void call_icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
+{
+	void (*func)(struct sk_buff *skb, u8 type, u8 code, __u32 info);
+
+	func = rcu_dereference(icmpv6_send_ptr);
+	if (func)
+		(*func)(skb, type, code, info);
+}
+EXPORT_SYMBOL(call_icmpv6_send);
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 35c93e8..6cbd37c 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -788,7 +788,7 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
 		}
 
 		if (mtu >= IPV6_MIN_MTU && mtu < skb->len - tunnel->hlen + gre_hlen) {
-			icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
+			call_icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
 			ip_rt_put(rt);
 			goto tx_error;
 		}
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 03e62f9..25e9ad6 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -862,6 +862,7 @@ int __init icmpv6_init(void)
 	err = -EAGAIN;
 	if (inet6_add_protocol(&icmpv6_protocol, IPPROTO_ICMPV6) < 0)
 		goto fail;
+	register_icmpv6_send(icmpv6_send);
 	return 0;
 
 fail:
@@ -874,6 +875,7 @@ void icmpv6_cleanup(void)
 {
 	unregister_pernet_subsys(&icmpv6_sk_ops);
 	inet6_del_protocol(&icmpv6_protocol, IPPROTO_ICMPV6);
+	unregister_icmpv6_send();
 }