This allows us to forward packets from the netdev family via neighbour
layer, so you don't need an explicit link-layer destination when using
this expression from rules. The ttl/hop_limit field is decremented.
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
---
v3: - dev_get_by_index_rcu() after ttl/hop_limit decrement.
- calm down gcc warning reported by kbuild robot.
- redundant priv->nfproto initialization.
include/uapi/linux/netfilter/nf_tables.h | 4 +
net/netfilter/nft_fwd_netdev.c | 146 ++++++++++++++++++++++++++++++-
2 files changed, 149 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/netfilter/nf_tables.h
b/include/uapi/linux/netfilter/nf_tables.h
index 5c7eb9b9f6d6..a089af092a29 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -1260,10 +1260,14 @@ enum nft_dup_attributes {
* enum nft_fwd_attributes - nf_tables fwd expression netlink attributes
*
* @NFTA_FWD_SREG_DEV: source register of output interface (NLA_U32:
nft_register)
+ * @NFTA_FWD_SREG_ADDR: source register of destination address (NLA_U32:
nft_register)
+ * @NFTA_FWD_NFPROTO: layer 3 family of source register address (NLA_U32: enum
nfproto)
*/
enum nft_fwd_attributes {
NFTA_FWD_UNSPEC,
NFTA_FWD_SREG_DEV,
+ NFTA_FWD_SREG_ADDR,
+ NFTA_FWD_NFPROTO,
__NFTA_FWD_MAX
};
#define NFTA_FWD_MAX (__NFTA_FWD_MAX - 1)
diff --git a/net/netfilter/nft_fwd_netdev.c b/net/netfilter/nft_fwd_netdev.c
index ce13a50b9189..8abb9891cdf2 100644
--- a/net/netfilter/nft_fwd_netdev.c
+++ b/net/netfilter/nft_fwd_netdev.c
@@ -12,8 +12,12 @@
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nf_dup_netdev.h>
+#include <net/neighbour.h>
+#include <net/ip.h>
struct nft_fwd_netdev {
enum nft_registers sreg_dev:8;
@@ -32,6 +36,8 @@ static void nft_fwd_netdev_eval(const struct nft_expr *expr,
static const struct nla_policy nft_fwd_netdev_policy[NFTA_FWD_MAX + 1] = {
[NFTA_FWD_SREG_DEV] = { .type = NLA_U32 },
+ [NFTA_FWD_SREG_ADDR] = { .type = NLA_U32 },
+ [NFTA_FWD_NFPROTO] = { .type = NLA_U32 },
};
static int nft_fwd_netdev_init(const struct nft_ctx *ctx,
@@ -62,7 +68,133 @@ static int nft_fwd_netdev_dump(struct sk_buff *skb, const
struct nft_expr *expr)
return -1;
}
+struct nft_fwd_neigh {
+ enum nft_registers sreg_dev:8;
+ enum nft_registers sreg_addr:8;
+ u8 nfproto;
+};
+
+static void nft_fwd_neigh_eval(const struct nft_expr *expr,
+ struct nft_regs *regs,
+ const struct nft_pktinfo *pkt)
+{
+ struct nft_fwd_neigh *priv = nft_expr_priv(expr);
+ void *addr = ®s->data[priv->sreg_addr];
+ int oif = regs->data[priv->sreg_dev];
+ unsigned int verdict = NF_STOLEN;
+ struct sk_buff *skb = pkt->skb;
+ struct net_device *dev;
+ int neigh_table;
+
+ switch (priv->nfproto) {
+ case NFPROTO_IPV4: {
+ struct iphdr *iph;
+
+ if (skb->protocol != htons(ETH_P_IP)) {
+ verdict = NFT_BREAK;
+ goto out;
+ }
+ if (skb_try_make_writable(skb, sizeof(*iph))) {
+ verdict = NF_DROP;
+ goto out;
+ }
+ iph = ip_hdr(skb);
+ ip_decrease_ttl(iph);
+ neigh_table = NEIGH_ARP_TABLE;
+ break;
+ }
+ case NFPROTO_IPV6: {
+ struct ipv6hdr *ip6h;
+
+ if (skb->protocol != htons(ETH_P_IPV6)) {
+ verdict = NFT_BREAK;
+ goto out;
+ }
+ if (skb_try_make_writable(skb, sizeof(*ip6h))) {
+ verdict = NF_DROP;
+ goto out;
+ }
+ ip6h = ipv6_hdr(skb);
+ ip6h->hop_limit--;
+ neigh_table = NEIGH_ND_TABLE;
+ break;
+ }
+ default:
+ verdict = NFT_BREAK;
+ goto out;
+ }
+
+ dev = dev_get_by_index_rcu(nft_net(pkt), oif);
+ if (dev == NULL)
+ return;
+
+ skb->dev = dev;
+ neigh_xmit(neigh_table, dev, addr, skb);
+out:
+ regs->verdict.code = verdict;
+}
+
+static int nft_fwd_neigh_init(const struct nft_ctx *ctx,
+ const struct nft_expr *expr,
+ const struct nlattr * const tb[])
+{
+ struct nft_fwd_neigh *priv = nft_expr_priv(expr);
+ unsigned int addr_len;
+ int err;
+
+ if (!tb[NFTA_FWD_SREG_DEV] ||
+ !tb[NFTA_FWD_SREG_ADDR] ||
+ !tb[NFTA_FWD_NFPROTO])
+ return -EINVAL;
+
+ priv->sreg_dev = nft_parse_register(tb[NFTA_FWD_SREG_DEV]);
+ priv->sreg_addr = nft_parse_register(tb[NFTA_FWD_SREG_ADDR]);
+ priv->nfproto = ntohl(nla_get_be32(tb[NFTA_FWD_NFPROTO]));
+
+ switch (priv->nfproto) {
+ case NFPROTO_IPV4:
+ addr_len = sizeof(struct in_addr);
+ break;
+ case NFPROTO_IPV6:
+ addr_len = sizeof(struct in6_addr);
+ break;
+ default:
+ return -EOPNOTSUPP;
+ }
+
+ err = nft_validate_register_load(priv->sreg_dev, sizeof(int));
+ if (err < 0)
+ return err;
+
+ return nft_validate_register_load(priv->sreg_addr, addr_len);
+}
+
+static const struct nft_expr_ops nft_fwd_netdev_ingress_ops;
+
+static int nft_fwd_neigh_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+ struct nft_fwd_neigh *priv = nft_expr_priv(expr);
+
+ if (nft_dump_register(skb, NFTA_FWD_SREG_DEV, priv->sreg_dev) ||
+ nft_dump_register(skb, NFTA_FWD_SREG_ADDR, priv->sreg_addr) ||
+ nla_put_be32(skb, NFTA_FWD_NFPROTO, htonl(priv->nfproto)))
+ goto nla_put_failure;
+
+ return 0;
+
+nla_put_failure:
+ return -1;
+}
+
static struct nft_expr_type nft_fwd_netdev_type;
+static const struct nft_expr_ops nft_fwd_neigh_netdev_ops = {
+ .type = &nft_fwd_netdev_type,
+ .size = NFT_EXPR_SIZE(sizeof(struct nft_fwd_neigh)),
+ .eval = nft_fwd_neigh_eval,
+ .init = nft_fwd_neigh_init,
+ .dump = nft_fwd_neigh_dump,
+};
+
static const struct nft_expr_ops nft_fwd_netdev_ops = {
.type = &nft_fwd_netdev_type,
.size = NFT_EXPR_SIZE(sizeof(struct nft_fwd_netdev)),
@@ -71,10 +203,22 @@ static const struct nft_expr_ops nft_fwd_netdev_ops = {
.dump = nft_fwd_netdev_dump,
};
+static const struct nft_expr_ops *
+nft_fwd_select_ops(const struct nft_ctx *ctx,
+ const struct nlattr * const tb[])
+{
+ if (tb[NFTA_FWD_SREG_ADDR])
+ return &nft_fwd_neigh_netdev_ops;
+ if (tb[NFTA_FWD_SREG_DEV])
+ return &nft_fwd_netdev_ops;
+
+ return ERR_PTR(-EOPNOTSUPP);
+}
+
static struct nft_expr_type nft_fwd_netdev_type __read_mostly = {
.family = NFPROTO_NETDEV,
.name = "fwd",
- .ops = &nft_fwd_netdev_ops,
+ .select_ops = nft_fwd_select_ops,
.policy = nft_fwd_netdev_policy,
.maxattr = NFTA_FWD_MAX,
.owner = THIS_MODULE,
--
2.11.0
--
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