netfilter: flow table support for IPv4
This patch adds the IPv4 flow table type, that implements the datapath flow table to forward IPv4 traffic. Rationale is: 1) Look up for the packet in the flow table, from the ingress hook. 2) If there's a hit, decrement ttl and pass it on to the neighbour layer for transmission. 3) If there's a miss, packet is passed up to the classic forwarding path. This patch also supports layer 3 source and destination NAT. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso
Родитель
ac2a66665e
Коммит
97add9f0d6
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@ -78,6 +78,14 @@ config NF_TABLES_ARP
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endif # NF_TABLES
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config NF_FLOW_TABLE_IPV4
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select NF_FLOW_TABLE
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tristate "Netfilter flow table IPv4 module"
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help
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This option adds the flow table IPv4 support.
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To compile it as a module, choose M here.
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config NF_DUP_IPV4
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tristate "Netfilter IPv4 packet duplication to alternate destination"
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depends on !NF_CONNTRACK || NF_CONNTRACK
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@ -43,6 +43,9 @@ obj-$(CONFIG_NFT_REDIR_IPV4) += nft_redir_ipv4.o
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obj-$(CONFIG_NFT_DUP_IPV4) += nft_dup_ipv4.o
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obj-$(CONFIG_NF_TABLES_ARP) += nf_tables_arp.o
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# flow table support
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obj-$(CONFIG_NF_FLOW_TABLE_IPV4) += nf_flow_table_ipv4.o
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# generic IP tables
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obj-$(CONFIG_IP_NF_IPTABLES) += ip_tables.o
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@ -0,0 +1,283 @@
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/netfilter.h>
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#include <linux/rhashtable.h>
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#include <linux/ip.h>
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#include <linux/netdevice.h>
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#include <net/ip.h>
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#include <net/neighbour.h>
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#include <net/netfilter/nf_flow_table.h>
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#include <net/netfilter/nf_tables.h>
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/* For layer 4 checksum field offset. */
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#include <linux/tcp.h>
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#include <linux/udp.h>
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static int nf_flow_nat_ip_tcp(struct sk_buff *skb, unsigned int thoff,
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__be32 addr, __be32 new_addr)
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{
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struct tcphdr *tcph;
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if (!pskb_may_pull(skb, thoff + sizeof(*tcph)) ||
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skb_try_make_writable(skb, thoff + sizeof(*tcph)))
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return -1;
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tcph = (void *)(skb_network_header(skb) + thoff);
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inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, true);
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return 0;
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}
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static int nf_flow_nat_ip_udp(struct sk_buff *skb, unsigned int thoff,
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__be32 addr, __be32 new_addr)
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{
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struct udphdr *udph;
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if (!pskb_may_pull(skb, thoff + sizeof(*udph)) ||
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skb_try_make_writable(skb, thoff + sizeof(*udph)))
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return -1;
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udph = (void *)(skb_network_header(skb) + thoff);
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if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
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inet_proto_csum_replace4(&udph->check, skb, addr,
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new_addr, true);
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if (!udph->check)
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udph->check = CSUM_MANGLED_0;
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}
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return 0;
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}
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static int nf_flow_nat_ip_l4proto(struct sk_buff *skb, struct iphdr *iph,
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unsigned int thoff, __be32 addr,
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__be32 new_addr)
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{
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switch (iph->protocol) {
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case IPPROTO_TCP:
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if (nf_flow_nat_ip_tcp(skb, thoff, addr, new_addr) < 0)
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return NF_DROP;
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break;
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case IPPROTO_UDP:
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if (nf_flow_nat_ip_udp(skb, thoff, addr, new_addr) < 0)
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return NF_DROP;
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break;
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}
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return 0;
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}
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static int nf_flow_snat_ip(const struct flow_offload *flow, struct sk_buff *skb,
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struct iphdr *iph, unsigned int thoff,
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enum flow_offload_tuple_dir dir)
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{
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__be32 addr, new_addr;
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switch (dir) {
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case FLOW_OFFLOAD_DIR_ORIGINAL:
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addr = iph->saddr;
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new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_v4.s_addr;
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iph->saddr = new_addr;
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break;
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case FLOW_OFFLOAD_DIR_REPLY:
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addr = iph->daddr;
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new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_v4.s_addr;
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iph->daddr = new_addr;
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break;
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default:
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return -1;
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}
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csum_replace4(&iph->check, addr, new_addr);
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return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
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}
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static int nf_flow_dnat_ip(const struct flow_offload *flow, struct sk_buff *skb,
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struct iphdr *iph, unsigned int thoff,
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enum flow_offload_tuple_dir dir)
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{
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__be32 addr, new_addr;
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switch (dir) {
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case FLOW_OFFLOAD_DIR_ORIGINAL:
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addr = iph->daddr;
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new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.src_v4.s_addr;
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iph->daddr = new_addr;
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break;
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case FLOW_OFFLOAD_DIR_REPLY:
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addr = iph->saddr;
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new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_v4.s_addr;
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iph->saddr = new_addr;
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break;
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default:
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return -1;
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}
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return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
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}
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static int nf_flow_nat_ip(const struct flow_offload *flow, struct sk_buff *skb,
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enum flow_offload_tuple_dir dir)
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{
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struct iphdr *iph = ip_hdr(skb);
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unsigned int thoff = iph->ihl * 4;
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if (flow->flags & FLOW_OFFLOAD_SNAT &&
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(nf_flow_snat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
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nf_flow_snat_ip(flow, skb, iph, thoff, dir) < 0))
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return -1;
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if (flow->flags & FLOW_OFFLOAD_DNAT &&
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(nf_flow_dnat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
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nf_flow_dnat_ip(flow, skb, iph, thoff, dir) < 0))
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return -1;
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return 0;
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}
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static bool ip_has_options(unsigned int thoff)
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{
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return thoff != sizeof(struct iphdr);
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}
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static int nf_flow_tuple_ip(struct sk_buff *skb, const struct net_device *dev,
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struct flow_offload_tuple *tuple)
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{
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struct flow_ports *ports;
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unsigned int thoff;
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struct iphdr *iph;
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if (!pskb_may_pull(skb, sizeof(*iph)))
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return -1;
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iph = ip_hdr(skb);
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thoff = iph->ihl * 4;
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if (ip_is_fragment(iph) ||
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unlikely(ip_has_options(thoff)))
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return -1;
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if (iph->protocol != IPPROTO_TCP &&
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iph->protocol != IPPROTO_UDP)
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return -1;
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thoff = iph->ihl * 4;
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if (!pskb_may_pull(skb, thoff + sizeof(*ports)))
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return -1;
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ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
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tuple->src_v4.s_addr = iph->saddr;
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tuple->dst_v4.s_addr = iph->daddr;
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tuple->src_port = ports->source;
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tuple->dst_port = ports->dest;
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tuple->l3proto = AF_INET;
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tuple->l4proto = iph->protocol;
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tuple->iifidx = dev->ifindex;
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return 0;
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}
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/* Based on ip_exceeds_mtu(). */
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static bool __nf_flow_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
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{
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if (skb->len <= mtu)
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return false;
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if ((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0)
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return false;
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if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu))
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return false;
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return true;
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}
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static bool nf_flow_exceeds_mtu(struct sk_buff *skb, const struct rtable *rt)
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{
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u32 mtu;
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mtu = ip_dst_mtu_maybe_forward(&rt->dst, true);
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if (__nf_flow_exceeds_mtu(skb, mtu))
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return true;
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return false;
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}
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static unsigned int
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nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
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const struct nf_hook_state *state)
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{
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struct flow_offload_tuple_rhash *tuplehash;
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struct nf_flowtable *flow_table = priv;
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struct flow_offload_tuple tuple = {};
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enum flow_offload_tuple_dir dir;
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struct flow_offload *flow;
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struct net_device *outdev;
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const struct rtable *rt;
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struct iphdr *iph;
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__be32 nexthop;
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if (skb->protocol != htons(ETH_P_IP))
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return NF_ACCEPT;
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if (nf_flow_tuple_ip(skb, state->in, &tuple) < 0)
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return NF_ACCEPT;
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tuplehash = flow_offload_lookup(flow_table, &tuple);
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if (tuplehash == NULL)
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return NF_ACCEPT;
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outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.oifidx);
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if (!outdev)
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return NF_ACCEPT;
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dir = tuplehash->tuple.dir;
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flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
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rt = (const struct rtable *)flow->tuplehash[dir].tuple.dst_cache;
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if (unlikely(nf_flow_exceeds_mtu(skb, rt)))
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return NF_ACCEPT;
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if (skb_try_make_writable(skb, sizeof(*iph)))
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return NF_DROP;
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if (flow->flags & (FLOW_OFFLOAD_SNAT | FLOW_OFFLOAD_DNAT) &&
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nf_flow_nat_ip(flow, skb, dir) < 0)
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return NF_DROP;
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flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
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iph = ip_hdr(skb);
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ip_decrease_ttl(iph);
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skb->dev = outdev;
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nexthop = rt_nexthop(rt, flow->tuplehash[!dir].tuple.src_v4.s_addr);
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neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
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return NF_STOLEN;
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}
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static struct nf_flowtable_type flowtable_ipv4 = {
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.family = NFPROTO_IPV4,
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.params = &nf_flow_offload_rhash_params,
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.gc = nf_flow_offload_work_gc,
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.hook = nf_flow_offload_ip_hook,
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.owner = THIS_MODULE,
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};
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static int __init nf_flow_ipv4_module_init(void)
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{
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nft_register_flowtable_type(&flowtable_ipv4);
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return 0;
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}
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static void __exit nf_flow_ipv4_module_exit(void)
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{
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nft_unregister_flowtable_type(&flowtable_ipv4);
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}
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module_init(nf_flow_ipv4_module_init);
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module_exit(nf_flow_ipv4_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
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MODULE_ALIAS_NF_FLOWTABLE(AF_INET);
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