netdev - [RFC PATCH net-next v2 2/5] flow_dissector: Add L2TPv3 dissectors

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Date:   Mon, 29 Aug 2022 11:44:09 +0200
From:   Wojciech Drewek <wojciech.drewek@...el.com>
To:     netdev@...r.kernel.org
Cc:     alexandr.lobakin@...el.com, jesse.brandeburg@...el.com,
        anthony.l.nguyen@...el.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        marcin.szycik@...ux.intel.com, michal.swiatkowski@...ux.intel.com,
        kurt@...utronix.de, boris.sukholitko@...adcom.com,
        vladbu@...dia.com, komachi.yoshiki@...il.com, paulb@...dia.com,
        baowen.zheng@...igine.com, louis.peens@...igine.com,
        simon.horman@...igine.com, pablo@...filter.org,
        maksym.glubokiy@...ision.eu, intel-wired-lan@...ts.osuosl.org,
        jchapman@...alix.com, gnault@...hat.com
Subject: [RFC PATCH net-next v2 2/5] flow_dissector: Add L2TPv3 dissectors

Allow to dissect L2TPv3 specific field which is:
- session ID (32 bits)

L2TPv3 might be transported over IP or over UDP,
this ipmplementation is only about L2TPv3 over IP.
IP protocold carries L2TPv3 when ip_proto is
IPPROTO_L2TP (115).

Signed-off-by: Wojciech Drewek <wojciech.drewek@...el.com>
---
 include/net/flow_dissector.h |  9 +++++++++
 net/core/flow_dissector.c    | 28 ++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index 6c74812d64b2..5ccf52ef8809 100644
--- a/include/net/flow_dissector.h
+++ b/include/net/flow_dissector.h
@@ -289,6 +289,14 @@ struct flow_dissector_key_pppoe {
 	__be16 type;
 };
 
+/**
+ * struct flow_dissector_key_l2tpv3:
+ * @session_id: identifier for a l2tp session
+ */
+struct flow_dissector_key_l2tpv3 {
+	__be32 session_id;
+};
+
 enum flow_dissector_key_id {
 	FLOW_DISSECTOR_KEY_CONTROL, /* struct flow_dissector_key_control */
 	FLOW_DISSECTOR_KEY_BASIC, /* struct flow_dissector_key_basic */
@@ -320,6 +328,7 @@ enum flow_dissector_key_id {
 	FLOW_DISSECTOR_KEY_HASH, /* struct flow_dissector_key_hash */
 	FLOW_DISSECTOR_KEY_NUM_OF_VLANS, /* struct flow_dissector_key_num_of_vlans */
 	FLOW_DISSECTOR_KEY_PPPOE, /* struct flow_dissector_key_pppoe */
+	FLOW_DISSECTOR_KEY_L2TPV3, /* struct flow_dissector_key_l2tpv3 */
 
 	FLOW_DISSECTOR_KEY_MAX,
 };
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 764c4cb3fe8f..dbd944de4129 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -204,6 +204,30 @@ static void __skb_flow_dissect_icmp(const struct sk_buff *skb,
 	skb_flow_get_icmp_tci(skb, key_icmp, data, thoff, hlen);
 }
 
+static void __skb_flow_dissect_l2tpv3(const struct sk_buff *skb,
+				      struct flow_dissector *flow_dissector,
+				      void *target_container, const void *data,
+				      int nhoff, int hlen)
+{
+	struct flow_dissector_key_l2tpv3 *key_l2tpv3;
+	struct {
+		__be32 session_id;
+	} *hdr, _hdr;
+
+	hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr), data, hlen, &_hdr);
+	if (!hdr)
+		return;
+
+	if (!dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_L2TPV3))
+		return;
+
+	key_l2tpv3 = skb_flow_dissector_target(flow_dissector,
+					       FLOW_DISSECTOR_KEY_L2TPV3,
+					       target_container);
+
+	key_l2tpv3->session_id = hdr->session_id;
+}
+
 void skb_flow_dissect_meta(const struct sk_buff *skb,
 			   struct flow_dissector *flow_dissector,
 			   void *target_container)
@@ -1497,6 +1521,10 @@ bool __skb_flow_dissect(const struct net *net,
 		__skb_flow_dissect_icmp(skb, flow_dissector, target_container,
 					data, nhoff, hlen);
 		break;
+	case IPPROTO_L2TP:
+		__skb_flow_dissect_l2tpv3(skb, flow_dissector, target_container,
+					  data, nhoff, hlen);
+		break;
 
 	default:
 		break;
-- 
2.31.1