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Commit 6b5dc98e authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
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netfilter: rt: add support to fetch path mss



to be used in combination with tcp option set support to mimic
iptables TCPMSS --clamp-mss-to-pmtu.

v2: Eric Dumazet points out dst must be initialized.

Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 99d1712b
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+2 −0
Original line number Diff line number Diff line
@@ -811,11 +811,13 @@ enum nft_meta_keys {
 * @NFT_RT_CLASSID: realm value of packet's route (skb->dst->tclassid)
 * @NFT_RT_NEXTHOP4: routing nexthop for IPv4
 * @NFT_RT_NEXTHOP6: routing nexthop for IPv6
 * @NFT_RT_TCPMSS: fetch current path tcp mss
 */
enum nft_rt_keys {
	NFT_RT_CLASSID,
	NFT_RT_NEXTHOP4,
	NFT_RT_NEXTHOP6,
	NFT_RT_TCPMSS,
};

/**
+66 −0
Original line number Diff line number Diff line
@@ -23,6 +23,42 @@ struct nft_rt {
	enum nft_registers	dreg:8;
};

static u16 get_tcpmss(const struct nft_pktinfo *pkt, const struct dst_entry *skbdst)
{
	u32 minlen = sizeof(struct ipv6hdr), mtu = dst_mtu(skbdst);
	const struct sk_buff *skb = pkt->skb;
	const struct nf_afinfo *ai;
	struct flowi fl;

	memset(&fl, 0, sizeof(fl));

	switch (nft_pf(pkt)) {
	case NFPROTO_IPV4:
		fl.u.ip4.daddr = ip_hdr(skb)->saddr;
		minlen = sizeof(struct iphdr);
		break;
	case NFPROTO_IPV6:
		fl.u.ip6.daddr = ipv6_hdr(skb)->saddr;
		break;
	}

	ai = nf_get_afinfo(nft_pf(pkt));
	if (ai) {
		struct dst_entry *dst = NULL;

		ai->route(nft_net(pkt), &dst, &fl, false);
		if (dst) {
			mtu = min(mtu, dst_mtu(dst));
			dst_release(dst);
		}
	}

	if (mtu <= minlen || mtu > 0xffff)
		return TCP_MSS_DEFAULT;

	return mtu - minlen;
}

static void nft_rt_get_eval(const struct nft_expr *expr,
			    struct nft_regs *regs,
			    const struct nft_pktinfo *pkt)
@@ -57,6 +93,9 @@ static void nft_rt_get_eval(const struct nft_expr *expr,
					 &ipv6_hdr(skb)->daddr),
		       sizeof(struct in6_addr));
		break;
	case NFT_RT_TCPMSS:
		nft_reg_store16(dest, get_tcpmss(pkt, dst));
		break;
	default:
		WARN_ON(1);
		goto err;
@@ -94,6 +133,9 @@ static int nft_rt_get_init(const struct nft_ctx *ctx,
	case NFT_RT_NEXTHOP6:
		len = sizeof(struct in6_addr);
		break;
	case NFT_RT_TCPMSS:
		len = sizeof(u16);
		break;
	default:
		return -EOPNOTSUPP;
	}
@@ -118,6 +160,29 @@ static int nft_rt_get_dump(struct sk_buff *skb,
	return -1;
}

static int nft_rt_validate(const struct nft_ctx *ctx, const struct nft_expr *expr,
			   const struct nft_data **data)
{
	const struct nft_rt *priv = nft_expr_priv(expr);
	unsigned int hooks;

	switch (priv->key) {
	case NFT_RT_NEXTHOP4:
	case NFT_RT_NEXTHOP6:
	case NFT_RT_CLASSID:
		return 0;
	case NFT_RT_TCPMSS:
		hooks = (1 << NF_INET_FORWARD) |
			(1 << NF_INET_LOCAL_OUT) |
			(1 << NF_INET_POST_ROUTING);
		break;
	default:
		return -EINVAL;
	}

	return nft_chain_validate_hooks(ctx->chain, hooks);
}

static struct nft_expr_type nft_rt_type;
static const struct nft_expr_ops nft_rt_get_ops = {
	.type		= &nft_rt_type,
@@ -125,6 +190,7 @@ static const struct nft_expr_ops nft_rt_get_ops = {
	.eval		= nft_rt_get_eval,
	.init		= nft_rt_get_init,
	.dump		= nft_rt_get_dump,
	.validate	= nft_rt_validate,
};

static struct nft_expr_type nft_rt_type __read_mostly = {