[NETFILTER]: PPTP conntrack: fix another GRE keymap leak

When the master PPTP connection times out while still having unfullfilled
expectations (and a GRE keymap entry) associated with it, the keymap entry
is not destroyed.

Add a destroy callback to struct ip_conntrack_helper and use it to destroy
PPTP siblings when the master is destroyed.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter_ipv4/ip_conntrack_helper.h

@@ -25,6 +25,8 @@ struct ip_conntrack_helper
 		    struct ip_conntrack *ct,
 		    enum ip_conntrack_info conntrackinfo);
 
+	void (*destroy)(struct ip_conntrack *ct);
+
 	int (*to_nfattr)(struct sk_buff *skb, const struct ip_conntrack *ct);
 };
 

net/ipv4/netfilter/ip_conntrack_core.c

@@ -307,6 +307,7 @@ destroy_conntrack(struct nf_conntrack *nfct)
 {
 	struct ip_conntrack *ct = (struct ip_conntrack *)nfct;
 	struct ip_conntrack_protocol *proto;
+	struct ip_conntrack_helper *helper;
 
 	DEBUGP("destroy_conntrack(%p)\n", ct);
 	IP_NF_ASSERT(atomic_read(&nfct->use) == 0);
@@ -315,6 +316,10 @@ destroy_conntrack(struct nf_conntrack *nfct)
 	ip_conntrack_event(IPCT_DESTROY, ct);
 	set_bit(IPS_DYING_BIT, &ct->status);
 
+	helper = ct->helper;
+	if (helper && helper->destroy)
+		helper->destroy(ct);
+
 	/* To make sure we don't get any weird locking issues here:
 	 * destroy_conntrack() MUST NOT be called with a write lock
 	 * to ip_conntrack_lock!!! -HW */

net/ipv4/netfilter/ip_conntrack_helper_pptp.c

@@ -553,15 +553,6 @@ conntrack_pptp_help(struct sk_buff **pskb,
 	nexthdr_off += tcph->doff * 4;
  	datalen = tcplen - tcph->doff * 4;
 
-	if (tcph->fin || tcph->rst) {
-		DEBUGP("RST/FIN received, timeouting GRE\n");
-		/* can't do this after real newnat */
-		info->cstate = PPTP_CALL_NONE;
-
-		/* untrack this call id, unexpect GRE packets */
-		pptp_destroy_siblings(ct);
-	}
-
 	pptph = skb_header_pointer(*pskb, nexthdr_off, sizeof(_pptph), &_pptph);
 	if (!pptph) {
 		DEBUGP("no full PPTP header, can't track\n");
@@ -640,7 +631,8 @@ static struct ip_conntrack_helper pptp = {
 			   .protonum = 0xff
 		 	 }
 		},
-	.help = conntrack_pptp_help
+	.help = conntrack_pptp_help,
+	.destroy = pptp_destroy_siblings,
 };
 
 extern void ip_ct_proto_gre_fini(void);