OpenWrt – Rev 2
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From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Sun, 7 Jan 2018 01:04:19 +0100
Subject: [PATCH] netfilter: flow table support for IPv6
This patch adds the IPv6 flow table type, that implements the datapath
flow table to forward IPv6 traffic.
This patch exports ip6_dst_mtu_forward() that is required to check for
mtu to pass up packets that need PMTUD handling to the classic
forwarding path.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
create mode 100644 net/ipv6/netfilter/nf_flow_table_ipv6.c
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -889,6 +889,8 @@ static inline struct sk_buff *ip6_finish
&inet6_sk(sk)->cork);
}
+unsigned int ip6_dst_mtu_forward(const struct dst_entry *dst);
+
int ip6_dst_lookup(struct net *net, struct sock *sk, struct dst_entry **dst,
struct flowi6 *fl6);
struct dst_entry *ip6_dst_lookup_flow(const struct sock *sk, struct flowi6 *fl6,
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -381,7 +381,7 @@ static inline int ip6_forward_finish(str
return dst_output(net, sk, skb);
}
-static unsigned int ip6_dst_mtu_forward(const struct dst_entry *dst)
+unsigned int ip6_dst_mtu_forward(const struct dst_entry *dst)
{
unsigned int mtu;
struct inet6_dev *idev;
@@ -401,6 +401,7 @@ static unsigned int ip6_dst_mtu_forward(
return mtu;
}
+EXPORT_SYMBOL_GPL(ip6_dst_mtu_forward);
static bool ip6_pkt_too_big(const struct sk_buff *skb, unsigned int mtu)
{
--- a/net/ipv6/netfilter/Kconfig
+++ b/net/ipv6/netfilter/Kconfig
@@ -99,6 +99,14 @@ config NFT_FIB_IPV6
endif # NF_TABLES_IPV6
endif # NF_TABLES
+config NF_FLOW_TABLE_IPV6
+ select NF_FLOW_TABLE
+ tristate "Netfilter flow table IPv6 module"
+ help
+ This option adds the flow table IPv6 support.
+
+ To compile it as a module, choose M here.
+
config NF_DUP_IPV6
tristate "Netfilter IPv6 packet duplication to alternate destination"
depends on !NF_CONNTRACK || NF_CONNTRACK
--- a/net/ipv6/netfilter/Makefile
+++ b/net/ipv6/netfilter/Makefile
@@ -45,6 +45,9 @@ obj-$(CONFIG_NFT_REDIR_IPV6) += nft_redi
obj-$(CONFIG_NFT_DUP_IPV6) += nft_dup_ipv6.o
obj-$(CONFIG_NFT_FIB_IPV6) += nft_fib_ipv6.o
+# flow table support
+obj-$(CONFIG_NF_FLOW_TABLE_IPV6) += nf_flow_table_ipv6.o
+
# matches
obj-$(CONFIG_IP6_NF_MATCH_AH) += ip6t_ah.o
obj-$(CONFIG_IP6_NF_MATCH_EUI64) += ip6t_eui64.o
--- /dev/null
+++ b/net/ipv6/netfilter/nf_flow_table_ipv6.c
@@ -0,0 +1,277 @@
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/netfilter.h>
+#include <linux/rhashtable.h>
+#include <linux/ipv6.h>
+#include <linux/netdevice.h>
+#include <linux/ipv6.h>
+#include <net/ipv6.h>
+#include <net/ip6_route.h>
+#include <net/neighbour.h>
+#include <net/netfilter/nf_flow_table.h>
+#include <net/netfilter/nf_tables.h>
+/* For layer 4 checksum field offset. */
+#include <linux/tcp.h>
+#include <linux/udp.h>
+
+static int nf_flow_nat_ipv6_tcp(struct sk_buff *skb, unsigned int thoff,
+ struct in6_addr *addr,
+ struct in6_addr *new_addr)
+{
+ struct tcphdr *tcph;
+
+ if (!pskb_may_pull(skb, thoff + sizeof(*tcph)) ||
+ skb_try_make_writable(skb, thoff + sizeof(*tcph)))
+ return -1;
+
+ tcph = (void *)(skb_network_header(skb) + thoff);
+ inet_proto_csum_replace16(&tcph->check, skb, addr->s6_addr32,
+ new_addr->s6_addr32, true);
+
+ return 0;
+}
+
+static int nf_flow_nat_ipv6_udp(struct sk_buff *skb, unsigned int thoff,
+ struct in6_addr *addr,
+ struct in6_addr *new_addr)
+{
+ struct udphdr *udph;
+
+ if (!pskb_may_pull(skb, thoff + sizeof(*udph)) ||
+ skb_try_make_writable(skb, thoff + sizeof(*udph)))
+ return -1;
+
+ udph = (void *)(skb_network_header(skb) + thoff);
+ if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
+ inet_proto_csum_replace16(&udph->check, skb, addr->s6_addr32,
+ new_addr->s6_addr32, true);
+ if (!udph->check)
+ udph->check = CSUM_MANGLED_0;
+ }
+
+ return 0;
+}
+
+static int nf_flow_nat_ipv6_l4proto(struct sk_buff *skb, struct ipv6hdr *ip6h,
+ unsigned int thoff, struct in6_addr *addr,
+ struct in6_addr *new_addr)
+{
+ switch (ip6h->nexthdr) {
+ case IPPROTO_TCP:
+ if (nf_flow_nat_ipv6_tcp(skb, thoff, addr, new_addr) < 0)
+ return NF_DROP;
+ break;
+ case IPPROTO_UDP:
+ if (nf_flow_nat_ipv6_udp(skb, thoff, addr, new_addr) < 0)
+ return NF_DROP;
+ break;
+ }
+
+ return 0;
+}
+
+static int nf_flow_snat_ipv6(const struct flow_offload *flow,
+ struct sk_buff *skb, struct ipv6hdr *ip6h,
+ unsigned int thoff,
+ enum flow_offload_tuple_dir dir)
+{
+ struct in6_addr addr, new_addr;
+
+ switch (dir) {
+ case FLOW_OFFLOAD_DIR_ORIGINAL:
+ addr = ip6h->saddr;
+ new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_v6;
+ ip6h->saddr = new_addr;
+ break;
+ case FLOW_OFFLOAD_DIR_REPLY:
+ addr = ip6h->daddr;
+ new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_v6;
+ ip6h->daddr = new_addr;
+ break;
+ default:
+ return -1;
+ }
+
+ return nf_flow_nat_ipv6_l4proto(skb, ip6h, thoff, &addr, &new_addr);
+}
+
+static int nf_flow_dnat_ipv6(const struct flow_offload *flow,
+ struct sk_buff *skb, struct ipv6hdr *ip6h,
+ unsigned int thoff,
+ enum flow_offload_tuple_dir dir)
+{
+ struct in6_addr addr, new_addr;
+
+ switch (dir) {
+ case FLOW_OFFLOAD_DIR_ORIGINAL:
+ addr = ip6h->daddr;
+ new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.src_v6;
+ ip6h->daddr = new_addr;
+ break;
+ case FLOW_OFFLOAD_DIR_REPLY:
+ addr = ip6h->saddr;
+ new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_v6;
+ ip6h->saddr = new_addr;
+ break;
+ default:
+ return -1;
+ }
+
+ return nf_flow_nat_ipv6_l4proto(skb, ip6h, thoff, &addr, &new_addr);
+}
+
+static int nf_flow_nat_ipv6(const struct flow_offload *flow,
+ struct sk_buff *skb,
+ enum flow_offload_tuple_dir dir)
+{
+ struct ipv6hdr *ip6h = ipv6_hdr(skb);
+ unsigned int thoff = sizeof(*ip6h);
+
+ if (flow->flags & FLOW_OFFLOAD_SNAT &&
+ (nf_flow_snat_port(flow, skb, thoff, ip6h->nexthdr, dir) < 0 ||
+ nf_flow_snat_ipv6(flow, skb, ip6h, thoff, dir) < 0))
+ return -1;
+ if (flow->flags & FLOW_OFFLOAD_DNAT &&
+ (nf_flow_dnat_port(flow, skb, thoff, ip6h->nexthdr, dir) < 0 ||
+ nf_flow_dnat_ipv6(flow, skb, ip6h, thoff, dir) < 0))
+ return -1;
+
+ return 0;
+}
+
+static int nf_flow_tuple_ipv6(struct sk_buff *skb, const struct net_device *dev,
+ struct flow_offload_tuple *tuple)
+{
+ struct flow_ports *ports;
+ struct ipv6hdr *ip6h;
+ unsigned int thoff;
+
+ if (!pskb_may_pull(skb, sizeof(*ip6h)))
+ return -1;
+
+ ip6h = ipv6_hdr(skb);
+
+ if (ip6h->nexthdr != IPPROTO_TCP &&
+ ip6h->nexthdr != IPPROTO_UDP)
+ return -1;
+
+ thoff = sizeof(*ip6h);
+ if (!pskb_may_pull(skb, thoff + sizeof(*ports)))
+ return -1;
+
+ ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
+
+ tuple->src_v6 = ip6h->saddr;
+ tuple->dst_v6 = ip6h->daddr;
+ tuple->src_port = ports->source;
+ tuple->dst_port = ports->dest;
+ tuple->l3proto = AF_INET6;
+ tuple->l4proto = ip6h->nexthdr;
+ tuple->iifidx = dev->ifindex;
+
+ return 0;
+}
+
+/* Based on ip_exceeds_mtu(). */
+static bool __nf_flow_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
+{
+ if (skb->len <= mtu)
+ return false;
+
+ if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu))
+ return false;
+
+ return true;
+}
+
+static bool nf_flow_exceeds_mtu(struct sk_buff *skb, const struct rt6_info *rt)
+{
+ u32 mtu;
+
+ mtu = ip6_dst_mtu_forward(&rt->dst);
+ if (__nf_flow_exceeds_mtu(skb, mtu))
+ return true;
+
+ return false;
+}
+
+static unsigned int
+nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
+ const struct nf_hook_state *state)
+{
+ struct flow_offload_tuple_rhash *tuplehash;
+ struct nf_flowtable *flow_table = priv;
+ struct flow_offload_tuple tuple = {};
+ enum flow_offload_tuple_dir dir;
+ struct flow_offload *flow;
+ struct net_device *outdev;
+ struct in6_addr *nexthop;
+ struct ipv6hdr *ip6h;
+ struct rt6_info *rt;
+
+ if (skb->protocol != htons(ETH_P_IPV6))
+ return NF_ACCEPT;
+
+ if (nf_flow_tuple_ipv6(skb, state->in, &tuple) < 0)
+ return NF_ACCEPT;
+
+ tuplehash = flow_offload_lookup(flow_table, &tuple);
+ if (tuplehash == NULL)
+ return NF_ACCEPT;
+
+ outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.oifidx);
+ if (!outdev)
+ return NF_ACCEPT;
+
+ dir = tuplehash->tuple.dir;
+ flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
+
+ rt = (struct rt6_info *)flow->tuplehash[dir].tuple.dst_cache;
+ if (unlikely(nf_flow_exceeds_mtu(skb, rt)))
+ return NF_ACCEPT;
+
+ if (skb_try_make_writable(skb, sizeof(*ip6h)))
+ return NF_DROP;
+
+ if (flow->flags & (FLOW_OFFLOAD_SNAT | FLOW_OFFLOAD_DNAT) &&
+ nf_flow_nat_ipv6(flow, skb, dir) < 0)
+ return NF_DROP;
+
+ flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
+ ip6h = ipv6_hdr(skb);
+ ip6h->hop_limit--;
+
+ skb->dev = outdev;
+ nexthop = rt6_nexthop(rt, &flow->tuplehash[!dir].tuple.src_v6);
+ neigh_xmit(NEIGH_ND_TABLE, outdev, nexthop, skb);
+
+ return NF_STOLEN;
+}
+
+static struct nf_flowtable_type flowtable_ipv6 = {
+ .family = NFPROTO_IPV6,
+ .params = &nf_flow_offload_rhash_params,
+ .gc = nf_flow_offload_work_gc,
+ .hook = nf_flow_offload_ipv6_hook,
+ .owner = THIS_MODULE,
+};
+
+static int __init nf_flow_ipv6_module_init(void)
+{
+ nft_register_flowtable_type(&flowtable_ipv6);
+
+ return 0;
+}
+
+static void __exit nf_flow_ipv6_module_exit(void)
+{
+ nft_unregister_flowtable_type(&flowtable_ipv6);
+}
+
+module_init(nf_flow_ipv6_module_init);
+module_exit(nf_flow_ipv6_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
+MODULE_ALIAS_NF_FLOWTABLE(AF_INET6);
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