From: Florian Westphal fw@strlen.de
[ Upstream commit f92b40a8b2645af38bd6814651c59c1e690db53d ]
The netfilter NAT core cannot deal with more than one NAT hook per hook location (prerouting, input ...), because the NAT hooks install a NAT null binding in case the iptables nat table (iptable_nat hooks) or the corresponding nftables chain (nft nat hooks) doesn't specify a nat transformation.
Null bindings are needed to detect port collsisions between NAT-ed and non-NAT-ed connections.
This causes nftables NAT rules to not work when iptable_nat module is loaded, and vice versa because nat binding has already been attached when the second nat hook is consulted.
The netfilter core is not really the correct location to handle this (hooks are just hooks, the core has no notion of what kinds of side effects a hook implements), but its the only place where we can check for conflicts between both iptables hooks and nftables hooks without adding dependencies.
So add nat annotation to hook_ops to describe those hooks that will add NAT bindings and then make core reject if such a hook already exists. The annotation fills a padding hole, in case further restrictions appar we might change this to a 'u8 type' instead of bool.
iptables error if nft nat hook active: iptables -t nat -A POSTROUTING -j MASQUERADE iptables v1.4.21: can't initialize iptables table `nat': File exists Perhaps iptables or your kernel needs to be upgraded.
nftables error if iptables nat table present: nft -f /etc/nftables/ipv4-nat /usr/etc/nftables/ipv4-nat:3:1-2: Error: Could not process rule: File exists table nat { ^^
Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- include/linux/netfilter.h | 1 + net/ipv4/netfilter/iptable_nat.c | 4 ++++ net/ipv6/netfilter/ip6table_nat.c | 4 ++++ net/netfilter/core.c | 6 ++++++ net/netfilter/nf_tables_api.c | 2 ++ 5 files changed, 17 insertions(+)
diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h index b24e9b101651..267954bca56f 100644 --- a/include/linux/netfilter.h +++ b/include/linux/netfilter.h @@ -67,6 +67,7 @@ struct nf_hook_ops { struct net_device *dev; void *priv; u_int8_t pf; + bool nat_hook; unsigned int hooknum; /* Hooks are ordered in ascending priority. */ int priority; diff --git a/net/ipv4/netfilter/iptable_nat.c b/net/ipv4/netfilter/iptable_nat.c index a1a07b338ccf..0f7255cc65ee 100644 --- a/net/ipv4/netfilter/iptable_nat.c +++ b/net/ipv4/netfilter/iptable_nat.c @@ -72,6 +72,7 @@ static const struct nf_hook_ops nf_nat_ipv4_ops[] = { { .hook = iptable_nat_ipv4_in, .pf = NFPROTO_IPV4, + .nat_hook = true, .hooknum = NF_INET_PRE_ROUTING, .priority = NF_IP_PRI_NAT_DST, }, @@ -79,6 +80,7 @@ static const struct nf_hook_ops nf_nat_ipv4_ops[] = { { .hook = iptable_nat_ipv4_out, .pf = NFPROTO_IPV4, + .nat_hook = true, .hooknum = NF_INET_POST_ROUTING, .priority = NF_IP_PRI_NAT_SRC, }, @@ -86,6 +88,7 @@ static const struct nf_hook_ops nf_nat_ipv4_ops[] = { { .hook = iptable_nat_ipv4_local_fn, .pf = NFPROTO_IPV4, + .nat_hook = true, .hooknum = NF_INET_LOCAL_OUT, .priority = NF_IP_PRI_NAT_DST, }, @@ -93,6 +96,7 @@ static const struct nf_hook_ops nf_nat_ipv4_ops[] = { { .hook = iptable_nat_ipv4_fn, .pf = NFPROTO_IPV4, + .nat_hook = true, .hooknum = NF_INET_LOCAL_IN, .priority = NF_IP_PRI_NAT_SRC, }, diff --git a/net/ipv6/netfilter/ip6table_nat.c b/net/ipv6/netfilter/ip6table_nat.c index 991512576c8c..47306e45a80a 100644 --- a/net/ipv6/netfilter/ip6table_nat.c +++ b/net/ipv6/netfilter/ip6table_nat.c @@ -74,6 +74,7 @@ static const struct nf_hook_ops nf_nat_ipv6_ops[] = { { .hook = ip6table_nat_in, .pf = NFPROTO_IPV6, + .nat_hook = true, .hooknum = NF_INET_PRE_ROUTING, .priority = NF_IP6_PRI_NAT_DST, }, @@ -81,6 +82,7 @@ static const struct nf_hook_ops nf_nat_ipv6_ops[] = { { .hook = ip6table_nat_out, .pf = NFPROTO_IPV6, + .nat_hook = true, .hooknum = NF_INET_POST_ROUTING, .priority = NF_IP6_PRI_NAT_SRC, }, @@ -88,12 +90,14 @@ static const struct nf_hook_ops nf_nat_ipv6_ops[] = { { .hook = ip6table_nat_local_fn, .pf = NFPROTO_IPV6, + .nat_hook = true, .hooknum = NF_INET_LOCAL_OUT, .priority = NF_IP6_PRI_NAT_DST, }, /* After packet filtering, change source */ { .hook = ip6table_nat_fn, + .nat_hook = true, .pf = NFPROTO_IPV6, .hooknum = NF_INET_LOCAL_IN, .priority = NF_IP6_PRI_NAT_SRC, diff --git a/net/netfilter/core.c b/net/netfilter/core.c index 52cd2901a097..11e39cb19441 100644 --- a/net/netfilter/core.c +++ b/net/netfilter/core.c @@ -135,6 +135,12 @@ nf_hook_entries_grow(const struct nf_hook_entries *old, ++i; continue; } + + if (reg->nat_hook && orig_ops[i]->nat_hook) { + kvfree(new); + return ERR_PTR(-EEXIST); + } + if (inserted || reg->priority > orig_ops[i]->priority) { new_ops[nhooks] = (void *)orig_ops[i]; new->hooks[nhooks] = old->hooks[i]; diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index 5b504aa653f5..d2168fc61038 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -1400,6 +1400,8 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask, ops->hook = hookfn; if (afi->hook_ops_init) afi->hook_ops_init(ops, i); + if (basechain->type->type == NFT_CHAIN_T_NAT) + ops->nat_hook = true; }
chain->flags |= NFT_BASE_CHAIN;