flow_dissector: Add PPPoE dissectors

Allow to dissect PPPoE specific fields which are:
- session ID (16 bits)
- ppp protocol (16 bits)
- type (16 bits) - this is PPPoE ethertype, for now only
  ETH_P_PPP_SES is supported, possible ETH_P_PPP_DISC
  in the future

The goal is to make the following TC command possible:

  # tc filter add dev ens6f0 ingress prio 1 protocol ppp_ses \
      flower \
        pppoe_sid 12 \
        ppp_proto ip \
      action drop

Note that only PPPoE Session is supported.

Signed-off-by: Wojciech Drewek <wojciech.drewek@intel.com>
Acked-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/include/linux/ppp_defs.h b/include/linux/ppp_defs.h
index 9d2b388fae1a..b7e57fdbd413 100644
--- a/include/linux/ppp_defs.h
+++ b/include/linux/ppp_defs.h
@@ -11,4 +11,18 @@
 #include <uapi/linux/ppp_defs.h>
 
 #define PPP_FCS(fcs, c) crc_ccitt_byte(fcs, c)
+
+/**
+ * ppp_proto_is_valid - checks if PPP protocol is valid
+ * @proto: PPP protocol
+ *
+ * Assumes proto is not compressed.
+ * Protocol is valid if the value is odd and the least significant bit of the
+ * most significant octet is 0 (see RFC 1661, section 2).
+ */
+static inline bool ppp_proto_is_valid(u16 proto)
+{
+	return !!((proto & 0x0101) == 0x0001);
+}
+
 #endif /* _PPP_DEFS_H_ */