[lldp] Add support for the Link Layer Discovery Protocol

Add support for recording LLDP packets and exposing TLV values via the
settings mechanism.  LLDP settings are encoded as

  ${netX.lldp/<prefix>.<type>.<index>.<offset>.<length>}

where

  <type> is the TLV type

  <offset> is the starting offset within the TLV value

  <length> is the length (or zero to read the from <offset> to the end)

  <prefix>, if it has a non-zero value, is the subtype byte string of
  length <offset> to match at the start of the TLV value, up to a
  maximum matched length of 4 bytes

  <index> is the index of the entry matching <type> and <prefix> to be
  accessed, with zero indicating the first matching entry

The <prefix> is designed to accommodate both matching of the OUI
within an organization-specific TLV (e.g. 0x0080c2 for IEEE 802.1
TLVs) and of a subtype byte as found within many TLVs.

This encoding allows most LLDP values to be extracted easily.  For
example

  System name: ${netX.lldp/5.0.0.0:string}

  System description: ${netX.lldp/6.0.0.0:string}

  Port description: ${netX.lldp/4.0.0.0:string}

  Port interface name: ${netX.lldp/5.2.0.1.0:string}

  Chassis MAC address: ${netX.lldp/4.1.0.1.0:hex}

  Management IPv4 address: ${netX.lldp/5.1.8.0.2.4:ipv4}

  Port VLAN ID: ${netX.lldp/0x0080c2.1.127.0.4.2:int16}

  Port VLAN name: ${netX.lldp/0x0080c2.3.127.0.7.0:string}

  Maximum frame size: ${netX.lldp/0x00120f.4.127.0.4.2:uint16}

Originally-implemented-by: Marin Hannache <git@mareo.fr>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/errfile.h

@@ -295,6 +295,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_ntp			( ERRFILE_NET | 0x00490000 )
 #define ERRFILE_httpntlm		( ERRFILE_NET | 0x004a0000 )
 #define ERRFILE_eap			( ERRFILE_NET | 0x004b0000 )
+#define ERRFILE_lldp			( ERRFILE_NET | 0x004c0000 )
 
 #define ERRFILE_image		      ( ERRFILE_IMAGE | 0x00000000 )
 #define ERRFILE_elf		      ( ERRFILE_IMAGE | 0x00010000 )

src/include/ipxe/if_ether.h

@@ -23,6 +23,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ETH_P_SLOW	0x8809	/* Ethernet slow protocols */
 #define ETH_P_EAPOL	0x888E	/* 802.1X EAP over LANs */
 #define ETH_P_AOE	0x88A2	/* ATA over Ethernet */
+#define ETH_P_LLDP	0x88CC	/* Link Layer Discovery Protocol */
 #define ETH_P_FCOE	0x8906	/* Fibre Channel over Ethernet */
 #define ETH_P_FIP	0x8914	/* FCoE Initialization Protocol */
 

src/include/ipxe/lldp.h

@@ -0,0 +1,97 @@
+#ifndef _IPXE_LLDP_H
+#define _IPXE_LLDP_H
+
+/** @file
+ *
+ * Link Layer Discovery Protocol
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+
+/** An LLDP TLV header */
+struct lldp_tlv {
+	/** Type and length */
+	uint16_t type_len;
+	/** Data */
+	uint8_t data[0];
+} __attribute__ (( packed ));
+
+/**
+ * Extract LLDP TLV type
+ *
+ * @v type_len		Type and length
+ * @ret type		Type
+ */
+#define LLDP_TLV_TYPE( type_len ) ( (type_len) >> 9 )
+
+/**
+ * Extract LLDP TLV length
+ *
+ * @v type_len		Type and length
+ * @ret len		Length
+ */
+#define LLDP_TLV_LEN( type_len ) ( (type_len) & 0x01ff )
+
+/** End of LLDP data unit */
+#define LLDP_TYPE_END 0x00
+
+/** LLDP settings block name */
+#define LLDP_SETTINGS_NAME "lldp"
+
+/**
+ * Construct LLDP setting tag
+ *
+ * LLDP settings are encoded as
+ *
+ *   ${netX.lldp/<prefix>.<type>.<index>.<offset>.<length>}
+ *
+ * where
+ *
+ *   <type> is the TLV type
+ *
+ *   <offset> is the starting offset within the TLV value
+ *
+ *   <length> is the length (or zero to read the from <offset> to the end)
+ *
+ *   <prefix>, if it has a non-zero value, is the subtype byte string
+ *   of length <offset> to match at the start of the TLV value, up to
+ *   a maximum matched length of 4 bytes
+ *
+ *   <index> is the index of the entry matching <type> and <prefix> to
+ *   be accessed, with zero indicating the first matching entry
+ *
+ * The <prefix> is designed to accommodate both matching of the OUI
+ * within an organization-specific TLV (e.g. 0x0080c2 for IEEE 802.1
+ * TLVs) and of a subtype byte as found within many TLVs.
+ *
+ * This encoding allows most LLDP values to be extracted easily.  For
+ * example
+ *
+ *   System name: ${netX.lldp/5.0.0.0:string}
+ *
+ *   System description: ${netX.lldp/6.0.0.0:string}
+ *
+ *   Port description: ${netX.lldp/4.0.0.0:string}
+ *
+ *   Port interface name: ${netX.lldp/5.2.0.1.0:string}
+ *
+ *   Chassis MAC address: ${netX.lldp/4.1.0.1.0:hex}
+ *
+ *   Management IPv4 address: ${netX.lldp/5.1.8.0.2.4:ipv4}
+ *
+ *   Port VLAN ID: ${netX.lldp/0x0080c2.1.127.0.4.2:int16}
+ *
+ *   Port VLAN name: ${netX.lldp/0x0080c2.3.127.0.7.0:string}
+ *
+ *   Maximum frame size: ${netX.lldp/0x00120f.4.127.0.4.2:uint16}
+ *
+ */
+#define LLDP_TAG( prefix, type, index, offset, length )			\
+	( ( ( ( uint64_t ) (prefix) ) << 32 ) |				\
+	  ( (type) << 24 ) | ( (index) << 16 ) |			\
+	  ( (offset) << 8 ) | ( (length) << 0 ) )
+
+#endif /* _IPXE_LLDP_H */