Dear Netfilter Development Team,
I am following up on the patch I submitted almost two months ago (see below).
I would appreciate any updates on its review process or if any further action is required on my part to facilitate the review.
Best regards,
Daniel Pfeil
pda@xxxxxxxx
-----Ursprüngliche Nachricht-----
Von: pda Pfeil Daniel
Gesendet: Donnerstag, 25. April 2024 14:13
An: netfilter-devel@xxxxxxxxxxxxxxx
Betreff: [PATCH] conntrackd: helpers/rpc: Don't add expectation table entry for portmap port
After an RPC call to portmap using the portmap program number (100000), subsequent RPC calls are not handled correctly by connection tracking.
This results in client connections to ports specified in RPC replies failing to operate.
This issue arises because after an RPC call to portmap using the program number 100000, conntrackd adds an expectation table entry for the portmap port (typically 111). Due to this expectation table entry, subsequent RPC call connections are treated as sibling connections. Due to kernel restrictions, the connection helper for sibling connections cannot be changed. This is enforced in the kernel's handling in "net/netfilter/nf_conntrack_netlink.c", within the "ctnetlink_change_helper" function, after the comment:
/* don't change helper of sibling connections */.
Due to this kernel restriction, the private RPC data (struct rpc_info) sent from conntrackd to kernel-space is discarded by the kernel.
To resolve this, the proposed change is to eliminate the creation of an expectation table entry for the portmap port. The portmap port has to be opened via an iptables/nftables rule anyway, so adding an expectation table entry for the portmap port is unnecessary.
Why do our existing clients make RPC calls using the portmap program number? They use these calls for cyclic keepalive messages to verify that the link between the client and server is operational.
Signed-Off-By: Daniel Pfeil <pda@xxxxxxxx>
---
src/helpers/rpc.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/src/helpers/rpc.c b/src/helpers/rpc.c index 732e9ba..d8e4903 100644
--- a/src/helpers/rpc.c
+++ b/src/helpers/rpc.c
@@ -399,6 +399,11 @@ rpc_helper_cb(struct pkt_buff *pkt, uint32_t protoff,
xid, rpc_info->xid);
goto out;
}
+ /* Ignore portmap program number */
+ if (rpc_info->pm_prog == PMAPPROG) {
+ pr_debug("RPC REPL: ignore portmap program number %lu\n", PMAPPROG);
+ goto out;
+ }
if (rpc_reply(data, offset, datalen, rpc_info, &port_ptr) < 0)
goto out;
--
2.30.2
