Merge branch 'flow_dissector-Provide-basic-batman-adv-unicast-handling'

Sven Eckelmann says:

====================
flow_dissector: Provide basic batman-adv unicast handling

we are currently starting to use batman-adv as mesh protocol on multicore
embedded devices. These usually don't have a lot of CPU power per core but
are reasonable fast when using multiple cores.

It was noticed that sending was working very well but receiving was
basically only using on CPU core per neighbor. The reason for that is
format of the (normal) incoming packet:

  +--------------------+
  | ip(v6)hdr          |
  +--------------------+
  | inner ethhdr       |
  +--------------------+
  | batadv unicast hdr |
  +--------------------+
  | outer ethhdr       |
  +--------------------+

The flow dissector will therefore stop after parsing the outer ethernet
header and will not parse the actual ipv(4|6)/... header of the packet. Our
assumption was now that it would help us to add minimal support to the flow
dissector to jump over the batman-adv unicast and inner ethernet header
(like in gre ETH_P_TEB). The patch was implemented in a slightly hacky
way [1] and the results looked quite promising.

I didn't get any feedback how the files should actually be named. So I am
now just using the names from RFC v3

The discussion of the RFC v3 can be found in the related patches of
https://patchwork.ozlabs.org/cover/849345/

The discussion of the RFC v2 can be found in the related patches of
https://patchwork.ozlabs.org/cover/844783/

Changes in v4:
==============

* added  patch to change the u8/u16 to __u8/__u16 in
  include/uapi/linux/batadv_packet.h
  - requested by Willem de Bruijn <willemdebruijn.kernel@gmail.com>

Changes in v3:
==============

* removed change of uapi/linux/batman_adv.h to uapi/linux/batadv_genl.h
  - requested by Willem de Bruijn <willemdebruijn.kernel@gmail.com>
* removed naming fixes for enums/defines in uapi/linux/batadv_genl.h
  - requested by Willem de Bruijn <willemdebruijn.kernel@gmail.com>
* renamed uapi/linux/batadv.h to uapi/linux/batadv_packet.h
* moved batadv dissector functionality in own function
  - requested by Tom Herbert <tom@herbertland.com>
* added support for flags FLOW_DISSECTOR_F_STOP_AT_ENCAP and
  FLOW_DIS_ENCAPSULATION
  - requested by Willem de Bruijn <willemdebruijn.kernel@gmail.com>

Changes in v2:
==============

* removed the batman-adv unicast packet header definition from flow_dissector.c
* moved the batman-adv packet.h/uapi headers around to provide the correct
  definitions to flow_dissector.c
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 57 insertions, 0 deletions

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index cc75488d3653..02db7b122a73 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -24,6 +24,7 @@
 #include <linux/tcp.h>
 #include <net/flow_dissector.h>
 #include <scsi/fc/fc_fcoe.h>
+#include <uapi/linux/batadv_packet.h>
 
 static void dissector_set_key(struct flow_dissector *flow_dissector,
 			      enum flow_dissector_key_id key_id)
@@ -437,6 +438,57 @@ __skb_flow_dissect_gre(const struct sk_buff *skb,
 	return FLOW_DISSECT_RET_PROTO_AGAIN;
 }
 
+/**
+ * __skb_flow_dissect_batadv() - dissect batman-adv header
+ * @skb: sk_buff to with the batman-adv header
+ * @key_control: flow dissectors control key
+ * @data: raw buffer pointer to the packet, if NULL use skb->data
+ * @p_proto: pointer used to update the protocol to process next
+ * @p_nhoff: pointer used to update inner network header offset
+ * @hlen: packet header length
+ * @flags: any combination of FLOW_DISSECTOR_F_*
+ *
+ * ETH_P_BATMAN packets are tried to be dissected. Only
+ * &struct batadv_unicast packets are actually processed because they contain an
+ * inner ethernet header and are usually followed by actual network header. This
+ * allows the flow dissector to continue processing the packet.
+ *
+ * Return: FLOW_DISSECT_RET_PROTO_AGAIN when &struct batadv_unicast was found,
+ *  FLOW_DISSECT_RET_OUT_GOOD when dissector should stop after encapsulation,
+ *  otherwise FLOW_DISSECT_RET_OUT_BAD
+ */
+static enum flow_dissect_ret
+__skb_flow_dissect_batadv(const struct sk_buff *skb,
+			  struct flow_dissector_key_control *key_control,
+			  void *data, __be16 *p_proto, int *p_nhoff, int hlen,
+			  unsigned int flags)
+{
+	struct {
+		struct batadv_unicast_packet batadv_unicast;
+		struct ethhdr eth;
+	} *hdr, _hdr;
+
+	hdr = __skb_header_pointer(skb, *p_nhoff, sizeof(_hdr), data, hlen,
+				   &_hdr);
+	if (!hdr)
+		return FLOW_DISSECT_RET_OUT_BAD;
+
+	if (hdr->batadv_unicast.version != BATADV_COMPAT_VERSION)
+		return FLOW_DISSECT_RET_OUT_BAD;
+
+	if (hdr->batadv_unicast.packet_type != BATADV_UNICAST)
+		return FLOW_DISSECT_RET_OUT_BAD;
+
+	*p_proto = hdr->eth.h_proto;
+	*p_nhoff += sizeof(*hdr);
+
+	key_control->flags |= FLOW_DIS_ENCAPSULATION;
+	if (flags & FLOW_DISSECTOR_F_STOP_AT_ENCAP)
+		return FLOW_DISSECT_RET_OUT_GOOD;
+
+	return FLOW_DISSECT_RET_PROTO_AGAIN;
+}
+
 static void
 __skb_flow_dissect_tcp(const struct sk_buff *skb,
 		       struct flow_dissector *flow_dissector,
@@ -815,6 +867,11 @@ proto_again:
 					       nhoff, hlen);
 		break;
 
+	case htons(ETH_P_BATMAN):
+		fdret = __skb_flow_dissect_batadv(skb, key_control, data,
+						  &proto, &nhoff, hlen, flags);
+		break;
+
 	default:
 		fdret = FLOW_DISSECT_RET_OUT_BAD;
 		break;