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/*
* Copyright (c) 2016 Anders K. Pedersen <akp@cohaesio.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/dst.h>
#include <net/ip6_route.h>
#include <net/route.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables_core.h>
struct nft_rt {
enum nft_rt_keys key:8;
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)
{
const struct nft_rt *priv = nft_expr_priv(expr);
const struct sk_buff *skb = pkt->skb;
u32 *dest = ®s->data[priv->dreg];
const struct dst_entry *dst;
dst = skb_dst(skb);
if (!dst)
goto err;
switch (priv->key) {
#ifdef CONFIG_IP_ROUTE_CLASSID
case NFT_RT_CLASSID:
*dest = dst->tclassid;
break;
#endif
case NFT_RT_NEXTHOP4:
if (nft_pf(pkt) != NFPROTO_IPV4)
goto err;
*dest = (__force u32)rt_nexthop((const struct rtable *)dst,
ip_hdr(skb)->daddr);
break;
case NFT_RT_NEXTHOP6:
if (nft_pf(pkt) != NFPROTO_IPV6)
goto err;
memcpy(dest, rt6_nexthop((struct rt6_info *)dst,
&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;
}
return;
err:
regs->verdict.code = NFT_BREAK;
}
static const struct nla_policy nft_rt_policy[NFTA_RT_MAX + 1] = {
[NFTA_RT_DREG] = { .type = NLA_U32 },
[NFTA_RT_KEY] = { .type = NLA_U32 },
};
static int nft_rt_get_init(const struct nft_ctx *ctx,
const struct nft_expr *expr,
const struct nlattr * const tb[])
{
struct nft_rt *priv = nft_expr_priv(expr);
unsigned int len;
if (tb[NFTA_RT_KEY] == NULL ||
tb[NFTA_RT_DREG] == NULL)
return -EINVAL;
priv->key = ntohl(nla_get_be32(tb[NFTA_RT_KEY]));
switch (priv->key) {
#ifdef CONFIG_IP_ROUTE_CLASSID
case NFT_RT_CLASSID:
#endif
case NFT_RT_NEXTHOP4:
len = sizeof(u32);
break;
case NFT_RT_NEXTHOP6:
len = sizeof(struct in6_addr);
break;
case NFT_RT_TCPMSS:
len = sizeof(u16);
break;
default:
return -EOPNOTSUPP;
}
priv->dreg = nft_parse_register(tb[NFTA_RT_DREG]);
return nft_validate_register_store(ctx, priv->dreg, NULL,
NFT_DATA_VALUE, len);
}
static int nft_rt_get_dump(struct sk_buff *skb,
const struct nft_expr *expr)
{
const struct nft_rt *priv = nft_expr_priv(expr);
if (nla_put_be32(skb, NFTA_RT_KEY, htonl(priv->key)))
goto nla_put_failure;
if (nft_dump_register(skb, NFTA_RT_DREG, priv->dreg))
goto nla_put_failure;
return 0;
nla_put_failure:
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,
.size = NFT_EXPR_SIZE(sizeof(struct nft_rt)),
.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 = {
.name = "rt",
.ops = &nft_rt_get_ops,
.policy = nft_rt_policy,
.maxattr = NFTA_RT_MAX,
.owner = THIS_MODULE,
};
static int __init nft_rt_module_init(void)
{
return nft_register_expr(&nft_rt_type);
}
static void __exit nft_rt_module_exit(void)
{
nft_unregister_expr(&nft_rt_type);
}
module_init(nft_rt_module_init);
module_exit(nft_rt_module_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Anders K. Pedersen <akp@cohaesio.com>");
MODULE_ALIAS_NFT_EXPR("rt");
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