From: Pablo Neira Ayuso 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 --- create mode 100644 net/ipv6/netfilter/nf_flow_table_ipv6.c --- a/include/net/ipv6.h +++ b/include/net/ipv6.h @@ -860,6 +860,8 @@ 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(struct net *net, 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 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +/* For layer 4 checksum field offset. */ +#include +#include + +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 "); +MODULE_ALIAS_NF_FLOWTABLE(AF_INET6);