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[Openvpn-devel,S] Change in openvpn[release/2.6]: dco: warn if DATA_V1 packets are sent to userspace

Message ID 7dc953fc5d0953c52e177890fb6563d0ec2211be-HTML@gerrit.openvpn.net
State Superseded
Headers show
Series [Openvpn-devel,S] Change in openvpn[release/2.6]: dco: warn if DATA_V1 packets are sent to userspace | expand

Commit Message

flichtenheld (Code Review) Oct. 7, 2023, 1:26 p.m. UTC 
Attention is currently required from: flichtenheld.

Hello flichtenheld,

I'd like you to do a code review.
Please visit

    http://gerrit.openvpn.net/c/openvpn/+/368?usp=email

to review the following change.


Change subject: dco: warn if DATA_V1 packets are sent to userspace
......................................................................

dco: warn if DATA_V1 packets are sent to userspace

Servers 2.4.0 - 2.4.4 support peer-id and AEAD ciphers,
but only send DATA_V1 packets. With DCO enabled on the
client, connection is established but not working.

This is because DCO driver(s) are unable to handle
DATA_V1 packets and forwards them to userspace, where
they silently disappear since crypto context is in
DCO and not in userspace.

Starting from 2.4.5 server sends DATA_V2 so problem
doesn't happen.

We cannot switch to non-DCO on the fly, so we log this
and advice user to upgrade the server to 2.4.5 or newer.

This fixes https://github.com/OpenVPN/openvpn/issues/422

Change-Id: I8cb2cb083e3cdadf187b7874979d79af3974e759
Signed-off-by: Lev Stipakov <lev@openvpn.net>
---
M src/openvpn/forward.c
1 file changed, 10 insertions(+), 2 deletions(-)



  git pull ssh://gerrit.openvpn.net:29418/openvpn refs/changes/68/368/1
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Patch

diff --git a/src/openvpn/forward.c b/src/openvpn/forward.c
index d8ad0d1..66843b4 100644
--- a/src/openvpn/forward.c
+++ b/src/openvpn/forward.c
@@ -1058,8 +1058,16 @@ 
              * and return false.
              */
             uint8_t opcode = *BPTR(&c->c2.buf) >> P_OPCODE_SHIFT;
-            if (tls_pre_decrypt(c->c2.tls_multi, &c->c2.from, &c->c2.buf, &co,
-                                floated, &ad_start))
+
+            if ((opcode == P_DATA_V1) && dco_enabled(&c->options))
+            {
+                msg(D_LINK_ERRORS,
+                    "Data Channel Offload doesn't support DATA_V1 packets. "
+                    "Upgrade your server to 2.4.5 or newer.");
+                c->c2.buf.len = 0;
+            }
+            else if (tls_pre_decrypt(c->c2.tls_multi, &c->c2.from, &c->c2.buf,
+                                     &co, floated, &ad_start))
             {
                 /* Restore pre-NCP frame parameters */
                 if (is_hard_reset_method2(opcode))