diff mbox series

[nf-next,v2] netfilter: nft_fwd_netdev: allow to forward packets via neighbour layer

Message ID 20180530235800.15637-1-pablo@netfilter.org
State Changes Requested
Delegated to: Pablo Neira
Headers show
Series [nf-next,v2] netfilter: nft_fwd_netdev: allow to forward packets via neighbour layer | expand

Commit Message

Pablo Neira Ayuso May 30, 2018, 11:58 p.m. UTC 
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 <pablo@netfilter.org>
---
v2: - Fix incorrect address source register validation.
    - Decrement ttl/hop_limit.
    - Fix incorrect nfproto initialization.
    - Missing nfproto field dump.

 include/uapi/linux/netfilter/nf_tables.h |   4 +
 net/netfilter/nft_fwd_netdev.c           | 146 ++++++++++++++++++++++++++++++-
 2 files changed, 149 insertions(+), 1 deletion(-)

Comments

kernel test robot June 1, 2018, 5:10 a.m. UTC | #1 
Hi Pablo,

I love your patch! Perhaps something to improve:

[auto build test WARNING on nf/master]
[also build test WARNING on v4.17-rc7 next-20180531]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Pablo-Neira-Ayuso/netfilter-nft_fwd_netdev-allow-to-forward-packets-via-neighbour-layer/20180601-093630
base:   https://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf.git master
config: i386-allmodconfig (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   net/netfilter/nft_fwd_netdev.c: In function 'nft_fwd_neigh_eval':
>> net/netfilter/nft_fwd_netdev.c:130:2: warning: 'neigh_table' may be used uninitialized in this function [-Wmaybe-uninitialized]
     neigh_xmit(neigh_table, dev, addr, skb);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

vim +/neigh_table +130 net/netfilter/nft_fwd_netdev.c

    76	
    77	static void nft_fwd_neigh_eval(const struct nft_expr *expr,
    78				      struct nft_regs *regs,
    79				      const struct nft_pktinfo *pkt)
    80	{
    81		struct nft_fwd_neigh *priv = nft_expr_priv(expr);
    82		void *addr = &regs->data[priv->sreg_addr];
    83		int oif = regs->data[priv->sreg_dev];
    84		unsigned int verdict = NF_STOLEN;
    85		struct sk_buff *skb = pkt->skb;
    86		struct net_device *dev;
    87		int neigh_table;
    88	
    89		dev = dev_get_by_index_rcu(nft_net(pkt), oif);
    90		if (dev == NULL)
    91			return;
    92	
    93		skb->dev = dev;
    94	
    95		switch (priv->nfproto) {
    96		case NFPROTO_IPV4: {
    97			struct iphdr *iph;
    98	
    99			if (skb->protocol != htons(ETH_P_IP)) {
   100				verdict = NFT_BREAK;
   101				goto out;
   102			}
   103			if (skb_try_make_writable(skb, sizeof(*iph))) {
   104				verdict = NF_DROP;
   105				goto out;
   106			}
   107			iph = ip_hdr(skb);
   108			ip_decrease_ttl(iph);
   109			neigh_table = NEIGH_ARP_TABLE;
   110			break;
   111			}
   112		case NFPROTO_IPV6: {
   113			struct ipv6hdr *ip6h;
   114	
   115			if (skb->protocol != htons(ETH_P_IPV6)) {
   116				verdict = NFT_BREAK;
   117				goto out;
   118			}
   119			if (skb_try_make_writable(skb, sizeof(*ip6h))) {
   120				verdict = NF_DROP;
   121				goto out;
   122			}
   123			ip6h = ipv6_hdr(skb);
   124			ip6h->hop_limit--;
   125			neigh_table = NEIGH_ND_TABLE;
   126			break;
   127			}
   128		}
   129	
 > 130		neigh_xmit(neigh_table, dev, addr, skb);
   131	out:
   132		regs->verdict.code = verdict;
   133	}
   134	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
diff mbox series

Patch

diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 9c71f024f9cc..dac77765a400 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -1230,10 +1230,14 @@  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..3d48a66bb6e5 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 = &regs->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;
+
+	dev = dev_get_by_index_rcu(nft_net(pkt), oif);
+	if (dev == NULL)
+		return;
+
+	skb->dev = dev;
+
+	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;
+		}
+	}
+
+	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:
+		priv->nfproto = NFPROTO_IPV4;
+		addr_len = sizeof(struct in_addr);
+		break;
+	case NFPROTO_IPV6:
+		priv->nfproto = 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,