| Message ID | 20220831134140.913337-2-arne@rfc2549.org |
|---|---|
| State | Accepted |
| Delegated to: | Gert Doering |
| Headers | show |
| Series | Stateless three-way handshake and control channel improvements | expand |
Hi, On Wed, Aug 31, 2022 at 03:41:40PM +0200, Arne Schwabe wrote: > This behaviour has been fixed on the Softether side with commit 37aa1ba5 [..] > + * in a packet (see commit a14d812dcbc in Softether) */ The code seems to do what the commit says, but seeing two different commit IDs here confuses me. gert
Acked-by: Gert Doering <gert@greenie.muc.de> This is straightforward. The detection "what makes a softether server?" is a bit annoying... and this code will be with us forever... I have not specifically tested this ("no softether server around") but ran the normal server/client tests. Your patch has been applied to the master branch. commit 036517d5e06c1254233d51893b3a196a3cd37492 Author: Arne Schwabe Date: Wed Aug 31 15:41:40 2022 +0200 Add workaround for Softether server dropping P_ACK_V1 with >= 5 acks Signed-off-by: Arne Schwabe <arne@rfc2549.org> Acked-by: Gert Doering <gert@greenie.muc.de> Message-Id: <20220831134140.913337-2-arne@rfc2549.org> URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg25142.html Signed-off-by: Gert Doering <gert@greenie.muc.de> -- kind regards, Gert Doering
diff --git a/src/openvpn/ssl_pkt.c b/src/openvpn/ssl_pkt.c index e86fbc1b8..9b180cbf4 100644 --- a/src/openvpn/ssl_pkt.c +++ b/src/openvpn/ssl_pkt.c @@ -177,6 +177,15 @@ write_control_auth(struct tls_session *session, { uint8_t header = ks->key_id | (opcode << P_OPCODE_SHIFT); + /* Workaround for Softether servers. Softether has a bug that it only + * allows 4 ACks in packets and drops packets if more ACKs are contained + * in a packet (see commit a14d812dcbc in Softether) */ + if (session->tls_wrap.mode == TLS_WRAP_NONE && !session->opt->server + && !(session->opt->crypto_flags & CO_USE_TLS_KEY_MATERIAL_EXPORT)) + { + max_ack = min_int(max_ack, 4); + } + ASSERT(link_socket_actual_defined(&ks->remote_addr)); ASSERT(reliable_ack_write (ks->rec_ack, ks->lru_acks, buf, &ks->session_id_remote,
Softether had the number of ACKs in ANY OpenVPN packet limited to 4 and dropped packets with more than 4 ACKs. This leads to Softether dropping P_ACK_V1 packets with more than 4 ACKs as invalid. As the recent change of always acking as many packets as possible, this leads to Softether server not being able to successfully establish a connection anymore as it never registers the ACKs. This behaviour has been fixed on the Softether side with commit 37aa1ba5 but in order to allow clients to connect to older Softether servers, this commit implements a workaround for the case that the peer might be a Softether server (no tls-auth/tls-crypt and no other advanced protocol feature) and limits ACKs to 4 in this case. Signed-off-by: Arne Schwabe <arne@rfc2549.org> --- src/openvpn/ssl_pkt.c | 9 +++++++++ 1 file changed, 9 insertions(+)