text: #ifndef _IPXE_TCPIP_H
  #define _IPXE_TCPIP_H
  
  /** @file
   *
   * Transport-network layer interface
   *
   */
  
  FILE_LICENCE ( GPL2_OR_LATER );
  
  #include <stdint.h>
  #include <ipxe/socket.h>
  #include <ipxe/in.h>
  #include <ipxe/tables.h>
  
  struct io_buffer;
  struct net_device;
  
  /** Empty checksum value
   *
   * This is the TCP/IP checksum over a zero-length block of data.
   */
  #define TCPIP_EMPTY_CSUM 0xffff
  
  /**
   * TCP/IP socket address
   *
   * This contains the fields common to socket addresses for all TCP/IP
   * address families.
   */
  struct sockaddr_tcpip {
  	/** Socket address family (part of struct @c sockaddr) */
  	sa_family_t st_family;
  	/** TCP/IP port */
  	uint16_t st_port;
  	/** Padding
  	 *
  	 * This ensures that a struct @c sockaddr_tcpip is large
  	 * enough to hold a socket address for any TCP/IP address
  	 * family.
  	 */
  	char pad[ sizeof ( struct sockaddr ) -
  		  ( sizeof ( sa_family_t ) + sizeof ( uint16_t ) ) ];
  } __attribute__ (( may_alias ));
  
  /** 
   * A transport-layer protocol of the TCP/IP stack (eg. UDP, TCP, etc)
   */
  struct tcpip_protocol {
  	/** Protocol name */
  	const char *name;
         	/**
           * Process received packet
           *
           * @v iobuf		I/O buffer
  	 * @v st_src		Partially-filled source address
  	 * @v st_dest		Partially-filled destination address
  	 * @v pshdr_csum	Pseudo-header checksum
  	 * @ret rc		Return status code
           *
           * This method takes ownership of the I/O buffer.
           */
          int ( * rx ) ( struct io_buffer *iobuf, struct sockaddr_tcpip *st_src,
  		       struct sockaddr_tcpip *st_dest, uint16_t pshdr_csum );
          /** 
  	 * Transport-layer protocol number
  	 *
  	 * This is a constant of the type IP_XXX
           */
          uint8_t tcpip_proto;
  };
  
  /**
   * A network-layer protocol of the TCP/IP stack (eg. IPV4, IPv6, etc)
   */
  struct tcpip_net_protocol {
  	/** Protocol name */
  	const char *name;
  	/** Network address family */
  	sa_family_t sa_family;
  	/**
  	 * Transmit packet
  	 *
  	 * @v iobuf		I/O buffer
  	 * @v tcpip_protocol	Transport-layer protocol
  	 * @v st_src		Source address, or NULL to use default
  	 * @v st_dest		Destination address
  	 * @v netdev		Network device (or NULL to route automatically)
  	 * @v trans_csum	Transport-layer checksum to complete, or NULL
  	 * @ret rc		Return status code
  	 *
  	 * This function takes ownership of the I/O buffer.
  	 */
  	int ( * tx ) ( struct io_buffer *iobuf,
  		       struct tcpip_protocol *tcpip_protocol,
  		       struct sockaddr_tcpip *st_src,
  		       struct sockaddr_tcpip *st_dest,
  		       struct net_device *netdev,
  		       uint16_t *trans_csum );
  };
  
  /** TCP/IP transport-layer protocol table */
  #define TCPIP_PROTOCOLS __table ( struct tcpip_protocol, "tcpip_protocols" )
  
  /** Declare a TCP/IP transport-layer protocol */
  #define __tcpip_protocol __table_entry ( TCPIP_PROTOCOLS, 01 )
  
  /** TCP/IP network-layer protocol table */
  #define TCPIP_NET_PROTOCOLS \
  	__table ( struct tcpip_net_protocol, "tcpip_net_protocols" )
  
  /** Declare a TCP/IP network-layer protocol */
  #define __tcpip_net_protocol __table_entry ( TCPIP_NET_PROTOCOLS, 01 )
  
  extern int tcpip_rx ( struct io_buffer *iobuf, uint8_t tcpip_proto,
  		      struct sockaddr_tcpip *st_src,
  		      struct sockaddr_tcpip *st_dest, uint16_t pshdr_csum );
  extern int tcpip_tx ( struct io_buffer *iobuf, struct tcpip_protocol *tcpip,
  		      struct sockaddr_tcpip *st_src,
  		      struct sockaddr_tcpip *st_dest,
  		      struct net_device *netdev,
  		      uint16_t *trans_csum );
  extern uint16_t tcpip_continue_chksum ( uint16_t partial,
  					const void *data, size_t len );
  extern uint16_t tcpip_chksum ( const void *data, size_t len );
  
  #endif /* _IPXE_TCPIP_H */
  