Re: [PATCH nf-next v3 3/4] netfilter: synproxy: extract SYNPROXY infrastructure from {ipt,ip6t}_SYNPROXY

[Florian Westphal <fw@strlen.de>]

Fernando Fernandez Mancera <ffmancera@riseup.net> wrote:
> +static void
> +synproxy_send_tcp_ipv6(struct net *net,
> +		       const struct sk_buff *skb, struct sk_buff *nskb,
> +		       struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
> +		       struct ipv6hdr *niph, struct tcphdr *nth,
> +		       unsigned int tcp_hdr_size)
> +{
> +	struct dst_entry *dst;
> +	struct flowi6 fl6;
> +
> +	nth->check = ~tcp_v6_check(tcp_hdr_size, &niph->saddr, &niph->daddr, 0);
> +	nskb->ip_summed   = CHECKSUM_PARTIAL;
> +	nskb->csum_start  = (unsigned char *)nth - nskb->head;
> +	nskb->csum_offset = offsetof(struct tcphdr, check);
> +
> +	memset(&fl6, 0, sizeof(fl6));
> +	fl6.flowi6_proto = IPPROTO_TCP;
> +	fl6.saddr = niph->saddr;
> +	fl6.daddr = niph->daddr;
> +	fl6.fl6_sport = nth->source;
> +	fl6.fl6_dport = nth->dest;
> +	security_skb_classify_flow((struct sk_buff *)skb,
> +				   flowi6_to_flowi(&fl6));
> +	dst = ip6_route_output(net, NULL, &fl6);

All good, BUT the above function call also pulls in ipv6.ko.
You can fold this patch to avoid it, it coverts it to use the
nf_ip6_route() wrapper which internally uses the v6ops pointer
for ip6_route_output if needed.

diff --git a/net/netfilter/nf_synproxy.c b/net/netfilter/nf_synproxy.c
--- a/net/netfilter/nf_synproxy.c
+++ b/net/netfilter/nf_synproxy.c
@@ -434,6 +434,7 @@ synproxy_send_tcp_ipv6(struct net *net,
 {
 	struct dst_entry *dst;
 	struct flowi6 fl6;
+	int err;
 
 	nth->check = ~tcp_v6_check(tcp_hdr_size, &niph->saddr, &niph->daddr, 0);
 	nskb->ip_summed   = CHECKSUM_PARTIAL;
@@ -448,11 +449,10 @@ synproxy_send_tcp_ipv6(struct net *net,
 	fl6.fl6_dport = nth->dest;
 	security_skb_classify_flow((struct sk_buff *)skb,
 				   flowi6_to_flowi(&fl6));
-	dst = ip6_route_output(net, NULL, &fl6);
-	if (dst->error) {
-		dst_release(dst);
+	err = nf_ip6_route(net, &dst, flowi6_to_flowi(&fl6), false);
+	if (err)
 		goto free_nskb;
-	}
+
 	dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
 	if (IS_ERR(dst))
 		goto free_nskb;