ipv6: hash net ptr into fragmentation bucket selection

As namespaces are sometimes used with overlapping ip address ranges,
we should also use the namespace as input to the hash to select the ip
fragmentation counter bucket.

Cc: Eric Dumazet <[e-mail]>
Cc: Flavio Leitner <[e-mail]>
Signed-off-by: Hannes Frederic Sowa <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/ipv6.h

···
 	return __ipv6_addr_diff(a1, a2, sizeof(struct in6_addr));
 }
 
-void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt);
-void ipv6_proxy_select_ident(struct sk_buff *skb);
+void ipv6_select_ident(struct net *net, struct frag_hdr *fhdr,
+		       struct rt6_info *rt);
+void ipv6_proxy_select_ident(struct net *net, struct sk_buff *skb);
 
 int ip6_dst_hoplimit(struct dst_entry *dst);
 

net/ipv6/ip6_output.c

···
 		skb_reset_network_header(skb);
 		memcpy(skb_network_header(skb), tmp_hdr, hlen);
 
-		ipv6_select_ident(fh, rt);
+		ipv6_select_ident(net, fh, rt);
 		fh->nexthdr = nexthdr;
 		fh->reserved = 0;
 		fh->frag_off = htons(IP6_MF);
···
 		fh->nexthdr = nexthdr;
 		fh->reserved = 0;
 		if (!frag_id) {
-			ipv6_select_ident(fh, rt);
+			ipv6_select_ident(net, fh, rt);
 			frag_id = fh->identification;
 		} else
 			fh->identification = frag_id;
···
 	skb_shinfo(skb)->gso_size = (mtu - fragheaderlen -
 				     sizeof(struct frag_hdr)) & ~7;
 	skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
-	ipv6_select_ident(&fhdr, rt);
+	ipv6_select_ident(sock_net(sk), &fhdr, rt);
 	skb_shinfo(skb)->ip6_frag_id = fhdr.identification;
 
 append:

net/ipv6/output_core.c

···
 #include <net/addrconf.h>
 #include <net/secure_seq.h>
 
-static u32 __ipv6_select_ident(u32 hashrnd, struct in6_addr *dst,
-			       struct in6_addr *src)
+static u32 __ipv6_select_ident(struct net *net, u32 hashrnd,
+			       struct in6_addr *dst, struct in6_addr *src)
 {
 	u32 hash, id;
 
 	hash = __ipv6_addr_jhash(dst, hashrnd);
 	hash = __ipv6_addr_jhash(src, hash);
+	hash ^= net_hash_mix(net);
 
 	/* Treat id of 0 as unset and if we get 0 back from ip_idents_reserve,
 	 * set the hight order instead thus minimizing possible future
···
  *
  * The network header must be set before calling this.
  */
-void ipv6_proxy_select_ident(struct sk_buff *skb)
+void ipv6_proxy_select_ident(struct net *net, struct sk_buff *skb)
 {
 	static u32 ip6_proxy_idents_hashrnd __read_mostly;
 	struct in6_addr buf[2];
···
 	net_get_random_once(&ip6_proxy_idents_hashrnd,
 			    sizeof(ip6_proxy_idents_hashrnd));
 
-	id = __ipv6_select_ident(ip6_proxy_idents_hashrnd,
+	id = __ipv6_select_ident(net, ip6_proxy_idents_hashrnd,
 				 &addrs[1], &addrs[0]);
 	skb_shinfo(skb)->ip6_frag_id = htonl(id);
 }
 EXPORT_SYMBOL_GPL(ipv6_proxy_select_ident);
 
-void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
+void ipv6_select_ident(struct net *net, struct frag_hdr *fhdr,
+		       struct rt6_info *rt)
 {
 	static u32 ip6_idents_hashrnd __read_mostly;
 	u32 id;
 
 	net_get_random_once(&ip6_idents_hashrnd, sizeof(ip6_idents_hashrnd));
 
-	id = __ipv6_select_ident(ip6_idents_hashrnd, &rt->rt6i_dst.addr,
+	id = __ipv6_select_ident(net, ip6_idents_hashrnd, &rt->rt6i_dst.addr,
 				 &rt->rt6i_src.addr);
 	fhdr->identification = htonl(id);
 }

net/ipv6/udp_offload.c

···
 
 		/* Set the IPv6 fragment id if not set yet */
 		if (!skb_shinfo(skb)->ip6_frag_id)
-			ipv6_proxy_select_ident(skb);
+			ipv6_proxy_select_ident(dev_net(skb->dev), skb);
 
 		segs = NULL;
 		goto out;
···
 		fptr->nexthdr = nexthdr;
 		fptr->reserved = 0;
 		if (!skb_shinfo(skb)->ip6_frag_id)
-			ipv6_proxy_select_ident(skb);
+			ipv6_proxy_select_ident(dev_net(skb->dev), skb);
 		fptr->identification = skb_shinfo(skb)->ip6_frag_id;
 
 		/* Fragment the skb. ipv6 header and the remaining fields of the