--- zzzz-none-000/linux-4.9.276/net/l2tp/l2tp_core.c	2021-07-20 14:21:16.000000000 +0000
+++ falcon-5530-750/linux-4.9.276/net/l2tp/l2tp_core.c	2023-04-05 08:19:02.000000000 +0000
@@ -815,8 +815,10 @@
 		}
 	}
 
-	/* Session data offset is defined only for L2TPv2 and is
-	 * indicated by an optional 16-bit value in the header.
+	/* Session data offset is handled differently for L2TPv2 and
+	 * L2TPv3. For L2TPv2, there is an optional 16-bit value in
+	 * the header. For L2TPv3, the offset is negotiated using AVPs
+	 * in the session setup control protocol.
 	 */
 	if (tunnel->version == L2TP_HDR_VER_2) {
 		/* If offset bit set, skip it. */
@@ -824,7 +826,8 @@
 			offset = ntohs(*(__be16 *)ptr);
 			ptr += 2 + offset;
 		}
-	}
+	} else
+		ptr += session->offset;
 
 	offset = ptr - optr;
 	if (!pskb_may_pull(skb, offset))
@@ -1111,6 +1114,8 @@
 		*((__be32 *)bufp) = htonl(l2h);
 		bufp += 4;
 	}
+	if (session->offset)
+		bufp += session->offset;
 
 	return bufp - optr;
 }
@@ -1197,7 +1202,7 @@
 	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 	IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
 			      IPSKB_REROUTED);
-	nf_reset(skb);
+	nf_reset_no_generic_ct(skb);
 
 	bh_lock_sock(sk);
 	if (sock_owned_by_user(sk)) {
@@ -1783,7 +1788,7 @@
 		if (session->send_seq)
 			session->hdr_len += 4;
 	} else {
-		session->hdr_len = 4 + session->cookie_len;
+		session->hdr_len = 4 + session->cookie_len + session->offset;
 		session->hdr_len += l2tp_get_l2specific_len(session);
 		if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
 			session->hdr_len += 4;
@@ -1834,6 +1839,7 @@
 			session->recv_seq = cfg->recv_seq;
 			session->lns_mode = cfg->lns_mode;
 			session->reorder_timeout = cfg->reorder_timeout;
+			session->offset = cfg->offset;
 			session->l2specific_type = cfg->l2specific_type;
 			session->l2specific_len = cfg->l2specific_len;
 			session->cookie_len = cfg->cookie_len;