netfilter: nf_tables: add netdev table to filter from ingress

This allows us to create netdev tables that contain ingress chains. Use
skb_header_pointer() as we may see shared sk_buffs at this stage.

This change provides access to the existing nf_tables features from the ingress
hook.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

4 files changed, 190 insertions, 0 deletions

diff --git a/include/net/netns/nftables.h b/include/net/netns/nftables.h
index eee608b12cc9..c80781146019 100644
--- a/include/net/netns/nftables.h
+++ b/include/net/netns/nftables.h
@@ -13,6 +13,7 @@ struct netns_nftables {
         struct nft_af_info      *inet;
         struct nft_af_info      *arp;
         struct nft_af_info      *bridge;
+        struct nft_af_info      *netdev;
         unsigned int            base_seq;
         u8                      gencursor;
 };
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 9a89e7c67d78..bd5aaebaa9a2 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -456,6 +456,11 @@ config NF_TABLES_INET
         help
           This option enables support for a mixed IPv4/IPv6 "inet" table.
 
+config NF_TABLES_NETDEV
+        tristate "Netfilter nf_tables netdev tables support"
+        help
+          This option enables support for the "netdev" table.
+
 config NFT_EXTHDR
         tristate "Netfilter nf_tables IPv6 exthdr module"
         help
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index a87d8b8ec730..70d026d46fe7 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -75,6 +75,7 @@ nf_tables-objs += nft_bitwise.o nft_byteorder.o nft_payload.o
 
 obj-$(CONFIG_NF_TABLES)         += nf_tables.o
 obj-$(CONFIG_NF_TABLES_INET)    += nf_tables_inet.o
+obj-$(CONFIG_NF_TABLES_NETDEV)  += nf_tables_netdev.o
 obj-$(CONFIG_NFT_COMPAT)        += nft_compat.o
 obj-$(CONFIG_NFT_EXTHDR)        += nft_exthdr.o
 obj-$(CONFIG_NFT_META)          += nft_meta.o
diff --git a/net/netfilter/nf_tables_netdev.c b/net/netfilter/nf_tables_netdev.c
new file mode 100644
index 000000000000..04cb17057f46
--- /dev/null
+++ b/net/netfilter/nf_tables_netdev.c
@@ -0,0 +1,183 @@
+/*
+ * Copyright (c) 2015 Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * 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/init.h>
+#include <linux/module.h>
+#include <net/netfilter/nf_tables.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <net/netfilter/nf_tables_ipv4.h>
+#include <net/netfilter/nf_tables_ipv6.h>
+
+static inline void
+nft_netdev_set_pktinfo_ipv4(struct nft_pktinfo *pkt,
+                            const struct nf_hook_ops *ops, struct sk_buff *skb,
+                            const struct nf_hook_state *state)
+{
+        struct iphdr *iph, _iph;
+        u32 len, thoff;
+
+        nft_set_pktinfo(pkt, ops, skb, state);
+
+        iph = skb_header_pointer(skb, skb_network_offset(skb), sizeof(*iph),
+                                 &_iph);
+        if (!iph)
+                return;
+
+        iph = ip_hdr(skb);
+        if (iph->ihl < 5 || iph->version != 4)
+                return;
+
+        len = ntohs(iph->tot_len);
+        thoff = iph->ihl * 4;
+        if (skb->len < len)
+                return;
+        else if (len < thoff)
+                return;
+
+        pkt->tprot = iph->protocol;
+        pkt->xt.thoff = thoff;
+        pkt->xt.fragoff = ntohs(iph->frag_off) & IP_OFFSET;
+}
+
+static inline void
+__nft_netdev_set_pktinfo_ipv6(struct nft_pktinfo *pkt,
+                              const struct nf_hook_ops *ops,
+                              struct sk_buff *skb,
+                              const struct nf_hook_state *state)
+{
+#if IS_ENABLED(CONFIG_IPV6)
+        struct ipv6hdr *ip6h, _ip6h;
+        unsigned int thoff = 0;
+        unsigned short frag_off;
+        int protohdr;
+        u32 pkt_len;
+
+        ip6h = skb_header_pointer(skb, skb_network_offset(skb), sizeof(*ip6h),
+                                  &_ip6h);
+        if (!ip6h)
+                return;
+
+        if (ip6h->version != 6)
+                return;
+
+        pkt_len = ntohs(ip6h->payload_len);
+        if (pkt_len + sizeof(*ip6h) > skb->len)
+                return;
+
+        protohdr = ipv6_find_hdr(pkt->skb, &thoff, -1, &frag_off, NULL);
+        if (protohdr < 0)
+                return;
+
+        pkt->tprot = protohdr;
+        pkt->xt.thoff = thoff;
+        pkt->xt.fragoff = frag_off;
+#endif
+}
+
+static inline void nft_netdev_set_pktinfo_ipv6(struct nft_pktinfo *pkt,
+                                               const struct nf_hook_ops *ops,
+                                               struct sk_buff *skb,
+                                               const struct nf_hook_state *state)
+{
+        nft_set_pktinfo(pkt, ops, skb, state);
+        __nft_netdev_set_pktinfo_ipv6(pkt, ops, skb, state);
+}
+
+static unsigned int
+nft_do_chain_netdev(const struct nf_hook_ops *ops, struct sk_buff *skb,
+                    const struct nf_hook_state *state)
+{
+        struct nft_pktinfo pkt;
+
+        switch (eth_hdr(skb)->h_proto) {
+        case htons(ETH_P_IP):
+                nft_netdev_set_pktinfo_ipv4(&pkt, ops, skb, state);
+                break;
+        case htons(ETH_P_IPV6):
+                nft_netdev_set_pktinfo_ipv6(&pkt, ops, skb, state);
+                break;
+        default:
+                nft_set_pktinfo(&pkt, ops, skb, state);
+                break;
+        }
+
+        return nft_do_chain(&pkt, ops);
+}
+
+static struct nft_af_info nft_af_netdev __read_mostly = {
+        .family         = NFPROTO_NETDEV,
+        .nhooks         = NF_NETDEV_NUMHOOKS,
+        .owner          = THIS_MODULE,
+        .flags          = NFT_AF_NEEDS_DEV,
+        .nops           = 1,
+        .hooks          = {
+                [NF_NETDEV_INGRESS]     = nft_do_chain_netdev,
+        },
+};
+
+static int nf_tables_netdev_init_net(struct net *net)
+{
+        net->nft.netdev = kmalloc(sizeof(struct nft_af_info), GFP_KERNEL);
+        if (net->nft.netdev == NULL)
+                return -ENOMEM;
+
+        memcpy(net->nft.netdev, &nft_af_netdev, sizeof(nft_af_netdev));
+
+        if (nft_register_afinfo(net, net->nft.netdev) < 0)
+                goto err;
+
+        return 0;
+err:
+        kfree(net->nft.netdev);
+        return -ENOMEM;
+}
+
+static void nf_tables_netdev_exit_net(struct net *net)
+{
+        nft_unregister_afinfo(net->nft.netdev);
+        kfree(net->nft.netdev);
+}
+
+static struct pernet_operations nf_tables_netdev_net_ops = {
+        .init   = nf_tables_netdev_init_net,
+        .exit   = nf_tables_netdev_exit_net,
+};
+
+static const struct nf_chain_type nft_filter_chain_netdev = {
+        .name           = "filter",
+        .type           = NFT_CHAIN_T_DEFAULT,
+        .family         = NFPROTO_NETDEV,
+        .owner          = THIS_MODULE,
+        .hook_mask      = (1 << NF_NETDEV_INGRESS),
+};
+
+static int __init nf_tables_netdev_init(void)
+{
+        int ret;
+
+        nft_register_chain_type(&nft_filter_chain_netdev);
+        ret = register_pernet_subsys(&nf_tables_netdev_net_ops);
+        if (ret < 0)
+                nft_unregister_chain_type(&nft_filter_chain_netdev);
+
+        return ret;
+}
+
+static void __exit nf_tables_netdev_exit(void)
+{
+        unregister_pernet_subsys(&nf_tables_netdev_net_ops);
+        nft_unregister_chain_type(&nft_filter_chain_netdev);
+}
+
+module_init(nf_tables_netdev_init);
+module_exit(nf_tables_netdev_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
+MODULE_ALIAS_NFT_FAMILY(5); /* NFPROTO_NETDEV */