From 8af79d3edb5fd2dce35ea0a71595b6d4f9962350 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Wed, 18 Sep 2024 15:13:39 +0200 Subject: netfilter: nfnetlink_queue: remove old clash resolution logic For historical reasons there are two clash resolution spots in netfilter, one in nfnetlink_queue and one in conntrack core. nfnetlink_queue one was added first: If a colliding entry is found, NAT NAT transformation is reversed by calling nat engine again with altered tuple. See commit 368982cd7d1b ("netfilter: nfnetlink_queue: resolve clash for unconfirmed conntracks") for details. One problem is that nf_reroute() won't take an action if the queueing doesn't occur in the OUTPUT hook, i.e. when queueing in forward or postrouting, packet will be sent via the wrong path. Another problem is that the scenario addressed (2nd UDP packet sent with identical addresses while first packet is still being processed) can also occur without any nfqueue involvement due to threaded resolvers doing A and AAAA requests back-to-back. This lead us to add clash resolution logic to the conntrack core, see commit 6a757c07e51f ("netfilter: conntrack: allow insertion of clashing entries"). Instead of fixing the nfqueue based logic, lets remove it and let conntrack core handle this instead. Retain the ->update hook for sake of nfqueue based conntrack helpers. We could axe this hook completely but we'd have to split confirm and helper logic again, see commit ee04805ff54a ("netfilter: conntrack: make conntrack userspace helpers work again"). This SHOULD NOT be backported to kernels earlier than v5.6; they lack adequate clash resolution handling. Patch was originally written by Pablo Neira Ayuso. Reported-by: Antonio Ojea Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1766 Signed-off-by: Florian Westphal Tested-by: Antonio Ojea Signed-off-by: Pablo Neira Ayuso --- include/linux/netfilter.h | 4 -- net/netfilter/nf_conntrack_core.c | 85 --------------------------------------- net/netfilter/nf_nat_core.c | 1 - 3 files changed, 90 deletions(-) diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h index 2683b2b77612..2b8aac2c70ad 100644 --- a/include/linux/netfilter.h +++ b/include/linux/netfilter.h @@ -376,15 +376,11 @@ int nf_route(struct net *net, struct dst_entry **dst, struct flowi *fl, struct nf_conn; enum nf_nat_manip_type; struct nlattr; -enum ip_conntrack_dir; struct nf_nat_hook { int (*parse_nat_setup)(struct nf_conn *ct, enum nf_nat_manip_type manip, const struct nlattr *attr); void (*decode_session)(struct sk_buff *skb, struct flowi *fl); - unsigned int (*manip_pkt)(struct sk_buff *skb, struct nf_conn *ct, - enum nf_nat_manip_type mtype, - enum ip_conntrack_dir dir); void (*remove_nat_bysrc)(struct nf_conn *ct); }; diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 7c63fbfb8c1d..9db3e2b0b1c3 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -2197,80 +2197,6 @@ static void nf_conntrack_attach(struct sk_buff *nskb, const struct sk_buff *skb) nf_conntrack_get(skb_nfct(nskb)); } -static int __nf_conntrack_update(struct net *net, struct sk_buff *skb, - struct nf_conn *ct, - enum ip_conntrack_info ctinfo) -{ - const struct nf_nat_hook *nat_hook; - struct nf_conntrack_tuple_hash *h; - struct nf_conntrack_tuple tuple; - unsigned int status; - int dataoff; - u16 l3num; - u8 l4num; - - l3num = nf_ct_l3num(ct); - - dataoff = get_l4proto(skb, skb_network_offset(skb), l3num, &l4num); - if (dataoff <= 0) - return NF_DROP; - - if (!nf_ct_get_tuple(skb, skb_network_offset(skb), dataoff, l3num, - l4num, net, &tuple)) - return NF_DROP; - - if (ct->status & IPS_SRC_NAT) { - memcpy(tuple.src.u3.all, - ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.all, - sizeof(tuple.src.u3.all)); - tuple.src.u.all = - ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.all; - } - - if (ct->status & IPS_DST_NAT) { - memcpy(tuple.dst.u3.all, - ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.all, - sizeof(tuple.dst.u3.all)); - tuple.dst.u.all = - ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u.all; - } - - h = nf_conntrack_find_get(net, nf_ct_zone(ct), &tuple); - if (!h) - return NF_ACCEPT; - - /* Store status bits of the conntrack that is clashing to re-do NAT - * mangling according to what it has been done already to this packet. - */ - status = ct->status; - - nf_ct_put(ct); - ct = nf_ct_tuplehash_to_ctrack(h); - nf_ct_set(skb, ct, ctinfo); - - nat_hook = rcu_dereference(nf_nat_hook); - if (!nat_hook) - return NF_ACCEPT; - - if (status & IPS_SRC_NAT) { - unsigned int verdict = nat_hook->manip_pkt(skb, ct, - NF_NAT_MANIP_SRC, - IP_CT_DIR_ORIGINAL); - if (verdict != NF_ACCEPT) - return verdict; - } - - if (status & IPS_DST_NAT) { - unsigned int verdict = nat_hook->manip_pkt(skb, ct, - NF_NAT_MANIP_DST, - IP_CT_DIR_ORIGINAL); - if (verdict != NF_ACCEPT) - return verdict; - } - - return NF_ACCEPT; -} - /* This packet is coming from userspace via nf_queue, complete the packet * processing after the helper invocation in nf_confirm(). */ @@ -2334,17 +2260,6 @@ static int nf_conntrack_update(struct net *net, struct sk_buff *skb) if (!ct) return NF_ACCEPT; - if (!nf_ct_is_confirmed(ct)) { - int ret = __nf_conntrack_update(net, skb, ct, ctinfo); - - if (ret != NF_ACCEPT) - return ret; - - ct = nf_ct_get(skb, &ctinfo); - if (!ct) - return NF_ACCEPT; - } - return nf_confirm_cthelper(skb, ct, ctinfo); } diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c index d9ea2c26f309..4085c436e306 100644 --- a/net/netfilter/nf_nat_core.c +++ b/net/netfilter/nf_nat_core.c @@ -1324,7 +1324,6 @@ static const struct nf_nat_hook nat_hook = { #ifdef CONFIG_XFRM .decode_session = __nf_nat_decode_session, #endif - .manip_pkt = nf_nat_manip_pkt, .remove_nat_bysrc = nf_nat_cleanup_conntrack, }; -- cgit v1.2.3-58-ga151