From: Andrii Melnychenko a.melnychenko@vyos.io
[ Upstream commit 90918e3b6404c2a37837b8f11692471b4c512de2 ]
Sequence adjustment may be required for FTP traffic with PASV/EPSV modes. due to need to re-write packet payload (IP, port) on the ftp control connection. This can require changes to the TCP length and expected seq / ack_seq.
The easiest way to reproduce this issue is with PASV mode. Example ruleset: table inet ftp_nat { ct helper ftp_helper { type "ftp" protocol tcp l3proto inet }
chain prerouting { type filter hook prerouting priority 0; policy accept; tcp dport 21 ct state new ct helper set "ftp_helper" } } table ip nat { chain prerouting { type nat hook prerouting priority -100; policy accept; tcp dport 21 dnat ip prefix to ip daddr map { 192.168.100.1 : 192.168.13.2/32 } }
chain postrouting { type nat hook postrouting priority 100 ; policy accept; tcp sport 21 snat ip prefix to ip saddr map { 192.168.13.2 : 192.168.100.1/32 } } }
Note that the ftp helper gets assigned *after* the dnat setup.
The inverse (nat after helper assign) is handled by an existing check in nf_nat_setup_info() and will not show the problem.
Topoloy:
+-------------------+ +----------------------------------+ | FTP: 192.168.13.2 | <-> | NAT: 192.168.13.3, 192.168.100.1 | +-------------------+ +----------------------------------+ | +-----------------------+ | Client: 192.168.100.2 | +-----------------------+
ftp nat changes do not work as expected in this case: Connected to 192.168.100.1. [..] ftp> epsv EPSV/EPRT on IPv4 off. ftp> ls 227 Entering passive mode (192,168,100,1,209,129). 421 Service not available, remote server has closed connection.
Kernel logs: Missing nfct_seqadj_ext_add() setup call WARNING: CPU: 1 PID: 0 at net/netfilter/nf_conntrack_seqadj.c:41 [..] __nf_nat_mangle_tcp_packet+0x100/0x160 [nf_nat] nf_nat_ftp+0x142/0x280 [nf_nat_ftp] help+0x4d1/0x880 [nf_conntrack_ftp] nf_confirm+0x122/0x2e0 [nf_conntrack] nf_hook_slow+0x3c/0xb0 ..
Fix this by adding the required extension when a conntrack helper is assigned to a connection that has a nat binding.
Fixes: 1a64edf54f55 ("netfilter: nft_ct: add helper set support") Signed-off-by: Andrii Melnychenko a.melnychenko@vyos.io Signed-off-by: Florian Westphal fw@strlen.de (cherry picked from commit 90918e3b6404c2a37837b8f11692471b4c512de2) [Harshit: Clean cherry-pick, apply it to stable-6.12.y] Signed-off-by: Harshit Mogalapalli harshit.m.mogalapalli@oracle.com --- net/netfilter/nft_ct.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c index a1b373b99f7b..58a6ad7ed7a4 100644 --- a/net/netfilter/nft_ct.c +++ b/net/netfilter/nft_ct.c @@ -22,6 +22,7 @@ #include <net/netfilter/nf_conntrack_timeout.h> #include <net/netfilter/nf_conntrack_l4proto.h> #include <net/netfilter/nf_conntrack_expect.h> +#include <net/netfilter/nf_conntrack_seqadj.h>
struct nft_ct_helper_obj { struct nf_conntrack_helper *helper4; @@ -1173,6 +1174,10 @@ static void nft_ct_helper_obj_eval(struct nft_object *obj, if (help) { rcu_assign_pointer(help->helper, to_assign); set_bit(IPS_HELPER_BIT, &ct->status); + + if ((ct->status & IPS_NAT_MASK) && !nfct_seqadj(ct)) + if (!nfct_seqadj_ext_add(ct)) + regs->verdict.code = NF_DROP; } }