/*
   * llc_pdu.c - access to PDU internals
   *
   * Copyright (c) 1997 by Procom Technology, Inc.
   *		 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   *
   * This program can be redistributed or modified under the terms of the
   * GNU General Public License as published by the Free Software Foundation.
   * This program is distributed without any warranty or implied warranty
   * of merchantability or fitness for a particular purpose.
   *
   * See the GNU General Public License for more details.
   */
  
  #include <linux/netdevice.h>
  #include <net/llc_pdu.h>
  
  static void llc_pdu_decode_pdu_type(struct sk_buff *skb, u8 *type);
  static u8 llc_pdu_get_pf_bit(struct llc_pdu_sn *pdu);
  
  void llc_pdu_set_cmd_rsp(struct sk_buff *skb, u8 pdu_type)
  {
  	llc_pdu_un_hdr(skb)->ssap |= pdu_type;
  }
  
  /**
   *	pdu_set_pf_bit - sets poll/final bit in LLC header
   *	@pdu_frame: input frame that p/f bit must be set into it.
   *	@bit_value: poll/final bit (0 or 1).
   *
   *	This function sets poll/final bit in LLC header (based on type of PDU).
   *	in I or S pdus, p/f bit is right bit of fourth byte in header. in U
   *	pdus p/f bit is fifth bit of third byte.
   */
  void llc_pdu_set_pf_bit(struct sk_buff *skb, u8 bit_value)
  {
  	u8 pdu_type;
  	struct llc_pdu_sn *pdu;
  
  	llc_pdu_decode_pdu_type(skb, &pdu_type);
  	pdu = llc_pdu_sn_hdr(skb);
  
  	switch (pdu_type) {
  	case LLC_PDU_TYPE_I:
  	case LLC_PDU_TYPE_S:
  		pdu->ctrl_2 = (pdu->ctrl_2 & 0xFE) | bit_value;
  		break;
  	case LLC_PDU_TYPE_U:
  		pdu->ctrl_1 |= (pdu->ctrl_1 & 0xEF) | (bit_value << 4);
  		break;
  	}
  }
  
  /**
   *	llc_pdu_decode_pf_bit - extracs poll/final bit from LLC header
   *	@skb: input skb that p/f bit must be extracted from it
   *	@pf_bit: poll/final bit (0 or 1)
   *
   *	This function extracts poll/final bit from LLC header (based on type of
   *	PDU). In I or S pdus, p/f bit is right bit of fourth byte in header. In
   *	U pdus p/f bit is fifth bit of third byte.
   */
  void llc_pdu_decode_pf_bit(struct sk_buff *skb, u8 *pf_bit)
  {
  	u8 pdu_type;
  	struct llc_pdu_sn *pdu;
  
  	llc_pdu_decode_pdu_type(skb, &pdu_type);
  	pdu = llc_pdu_sn_hdr(skb);
  
  	switch (pdu_type) {
  	case LLC_PDU_TYPE_I:
  	case LLC_PDU_TYPE_S:
  		*pf_bit = pdu->ctrl_2 & LLC_S_PF_BIT_MASK;
  		break;
  	case LLC_PDU_TYPE_U:
  		*pf_bit = (pdu->ctrl_1 & LLC_U_PF_BIT_MASK) >> 4;
  		break;
  	}
  }
  
  /**
   *	llc_pdu_init_as_disc_cmd - Builds DISC PDU
   *	@skb: Address of the skb to build
   *	@p_bit: The P bit to set in the PDU
   *
   *	Builds a pdu frame as a DISC command.
   */
  void llc_pdu_init_as_disc_cmd(struct sk_buff *skb, u8 p_bit)
  {
  	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_U;
  	pdu->ctrl_1 |= LLC_2_PDU_CMD_DISC;
  	pdu->ctrl_1 |= ((p_bit & 1) << 4) & LLC_U_PF_BIT_MASK;
  }
  
  /**
   *	llc_pdu_init_as_i_cmd - builds I pdu
   *	@skb: Address of the skb to build
   *	@p_bit: The P bit to set in the PDU
   *	@ns: The sequence number of the data PDU
   *	@nr: The seq. number of the expected I PDU from the remote
   *
   *	Builds a pdu frame as an I command.
   */
  void llc_pdu_init_as_i_cmd(struct sk_buff *skb, u8 p_bit, u8 ns, u8 nr)
  {
  	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_I;
  	pdu->ctrl_2  = 0;
  	pdu->ctrl_2 |= (p_bit & LLC_I_PF_BIT_MASK); /* p/f bit */
  	pdu->ctrl_1 |= (ns << 1) & 0xFE;   /* set N(S) in bits 2..8 */
  	pdu->ctrl_2 |= (nr << 1) & 0xFE;   /* set N(R) in bits 10..16 */
  }
  
  /**
   *	llc_pdu_init_as_rej_cmd - builds REJ PDU
   *	@skb: Address of the skb to build
   *	@p_bit: The P bit to set in the PDU
   *	@nr: The seq. number of the expected I PDU from the remote
   *
   *	Builds a pdu frame as a REJ command.
   */
  void llc_pdu_init_as_rej_cmd(struct sk_buff *skb, u8 p_bit, u8 nr)
  {
  	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_S;
  	pdu->ctrl_1 |= LLC_2_PDU_CMD_REJ;
  	pdu->ctrl_2  = 0;
  	pdu->ctrl_2 |= p_bit & LLC_S_PF_BIT_MASK;
  	pdu->ctrl_1 &= 0x0F;    /* setting bits 5..8 to zero(reserved) */
  	pdu->ctrl_2 |= (nr << 1) & 0xFE; /* set N(R) in bits 10..16 */
  }
  
  /**
   *	llc_pdu_init_as_rnr_cmd - builds RNR pdu
   *	@skb: Address of the skb to build
   *	@p_bit: The P bit to set in the PDU
   *	@nr: The seq. number of the expected I PDU from the remote
   *
   *	Builds a pdu frame as an RNR command.
   */
  void llc_pdu_init_as_rnr_cmd(struct sk_buff *skb, u8 p_bit, u8 nr)
  {
  	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_S;
  	pdu->ctrl_1 |= LLC_2_PDU_CMD_RNR;
  	pdu->ctrl_2  = 0;
  	pdu->ctrl_2 |= p_bit & LLC_S_PF_BIT_MASK;
  	pdu->ctrl_1 &= 0x0F;    /* setting bits 5..8 to zero(reserved) */
  	pdu->ctrl_2 |= (nr << 1) & 0xFE; /* set N(R) in bits 10..16 */
  }
  
  /**
   *	llc_pdu_init_as_rr_cmd - Builds RR pdu
   *	@skb: Address of the skb to build
   *	@p_bit: The P bit to set in the PDU
   *	@nr: The seq. number of the expected I PDU from the remote
   *
   *	Builds a pdu frame as an RR command.
   */
  void llc_pdu_init_as_rr_cmd(struct sk_buff *skb, u8 p_bit, u8 nr)
  {
  	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_S;
  	pdu->ctrl_1 |= LLC_2_PDU_CMD_RR;
  	pdu->ctrl_2  = p_bit & LLC_S_PF_BIT_MASK;
  	pdu->ctrl_1 &= 0x0F;    /* setting bits 5..8 to zero(reserved) */
  	pdu->ctrl_2 |= (nr << 1) & 0xFE; /* set N(R) in bits 10..16 */
  }
  
  /**
   *	llc_pdu_init_as_sabme_cmd - builds SABME pdu
   *	@skb: Address of the skb to build
   *	@p_bit: The P bit to set in the PDU
   *
   *	Builds a pdu frame as an SABME command.
   */
  void llc_pdu_init_as_sabme_cmd(struct sk_buff *skb, u8 p_bit)
  {
  	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_U;
  	pdu->ctrl_1 |= LLC_2_PDU_CMD_SABME;
  	pdu->ctrl_1 |= ((p_bit & 1) << 4) & LLC_U_PF_BIT_MASK;
  }
  
  /**
   *	llc_pdu_init_as_dm_rsp - builds DM response pdu
   *	@skb: Address of the skb to build
   *	@f_bit: The F bit to set in the PDU
   *
   *	Builds a pdu frame as a DM response.
   */
  void llc_pdu_init_as_dm_rsp(struct sk_buff *skb, u8 f_bit)
  {
  	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_U;
  	pdu->ctrl_1 |= LLC_2_PDU_RSP_DM;
  	pdu->ctrl_1 |= ((f_bit & 1) << 4) & LLC_U_PF_BIT_MASK;
  }
  
  /**
   *	llc_pdu_init_as_frmr_rsp - builds FRMR response PDU
   *	@skb: Address of the frame to build
   *	@prev_pdu: The rejected PDU frame
   *	@f_bit: The F bit to set in the PDU
   *	@vs: tx state vari value for the data link conn at the rejecting LLC
   *	@vr: rx state var value for the data link conn at the rejecting LLC
   *	@vzyxw: completely described in the IEEE Std 802.2 document (Pg 55)
   *
   *	Builds a pdu frame as a FRMR response.
   */
  void llc_pdu_init_as_frmr_rsp(struct sk_buff *skb, struct llc_pdu_sn *prev_pdu,
  			      u8 f_bit, u8 vs, u8 vr, u8 vzyxw)
  {
  	struct llc_frmr_info *frmr_info;
  	u8 prev_pf = 0;
  	u8 *ctrl;
  	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_U;
  	pdu->ctrl_1 |= LLC_2_PDU_RSP_FRMR;
  	pdu->ctrl_1 |= ((f_bit & 1) << 4) & LLC_U_PF_BIT_MASK;
  
  	frmr_info = (struct llc_frmr_info *)&pdu->ctrl_2;
  	ctrl = (u8 *)&prev_pdu->ctrl_1;
  	FRMR_INFO_SET_REJ_CNTRL(frmr_info,ctrl);
  	FRMR_INFO_SET_Vs(frmr_info, vs);
  	FRMR_INFO_SET_Vr(frmr_info, vr);
  	prev_pf = llc_pdu_get_pf_bit(prev_pdu);
  	FRMR_INFO_SET_C_R_BIT(frmr_info, prev_pf);
  	FRMR_INFO_SET_INVALID_PDU_CTRL_IND(frmr_info, vzyxw);
  	FRMR_INFO_SET_INVALID_PDU_INFO_IND(frmr_info, vzyxw);
  	FRMR_INFO_SET_PDU_INFO_2LONG_IND(frmr_info, vzyxw);
  	FRMR_INFO_SET_PDU_INVALID_Nr_IND(frmr_info, vzyxw);
  	FRMR_INFO_SET_PDU_INVALID_Ns_IND(frmr_info, vzyxw);
  	skb_put(skb, sizeof(struct llc_frmr_info));
  }
  
  /**
   *	llc_pdu_init_as_rr_rsp - builds RR response pdu
   *	@skb: Address of the skb to build
   *	@f_bit: The F bit to set in the PDU
   *	@nr: The seq. number of the expected data PDU from the remote
   *
   *	Builds a pdu frame as an RR response.
   */
  void llc_pdu_init_as_rr_rsp(struct sk_buff *skb, u8 f_bit, u8 nr)
  {
  	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_S;
  	pdu->ctrl_1 |= LLC_2_PDU_RSP_RR;
  	pdu->ctrl_2  = 0;
  	pdu->ctrl_2 |= f_bit & LLC_S_PF_BIT_MASK;
  	pdu->ctrl_1 &= 0x0F;    /* setting bits 5..8 to zero(reserved) */
  	pdu->ctrl_2 |= (nr << 1) & 0xFE;  /* set N(R) in bits 10..16 */
  }
  
  /**
   *	llc_pdu_init_as_rej_rsp - builds REJ response pdu
   *	@skb: Address of the skb to build
   *	@f_bit: The F bit to set in the PDU
   *	@nr: The seq. number of the expected data PDU from the remote
   *
   *	Builds a pdu frame as a REJ response.
   */
  void llc_pdu_init_as_rej_rsp(struct sk_buff *skb, u8 f_bit, u8 nr)
  {
  	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_S;
  	pdu->ctrl_1 |= LLC_2_PDU_RSP_REJ;
  	pdu->ctrl_2  = 0;
  	pdu->ctrl_2 |= f_bit & LLC_S_PF_BIT_MASK;
  	pdu->ctrl_1 &= 0x0F;    /* setting bits 5..8 to zero(reserved) */
  	pdu->ctrl_2 |= (nr << 1) & 0xFE;  /* set N(R) in bits 10..16 */
  }
  
  /**
   *	llc_pdu_init_as_rnr_rsp - builds RNR response pdu
   *	@skb: Address of the frame to build
   *	@f_bit: The F bit to set in the PDU
   *	@nr: The seq. number of the expected data PDU from the remote
   *
   *	Builds a pdu frame as an RNR response.
   */
  void llc_pdu_init_as_rnr_rsp(struct sk_buff *skb, u8 f_bit, u8 nr)
  {
  	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_S;
  	pdu->ctrl_1 |= LLC_2_PDU_RSP_RNR;
  	pdu->ctrl_2  = 0;
  	pdu->ctrl_2 |= f_bit & LLC_S_PF_BIT_MASK;
  	pdu->ctrl_1 &= 0x0F;    /* setting bits 5..8 to zero(reserved) */
  	pdu->ctrl_2 |= (nr << 1) & 0xFE;  /* set N(R) in bits 10..16 */
  }
  
  /**
   *	llc_pdu_init_as_ua_rsp - builds UA response pdu
   *	@skb: Address of the frame to build
   *	@f_bit: The F bit to set in the PDU
   *
   *	Builds a pdu frame as a UA response.
   */
  void llc_pdu_init_as_ua_rsp(struct sk_buff *skb, u8 f_bit)
  {
  	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
  
  	pdu->ctrl_1  = LLC_PDU_TYPE_U;
  	pdu->ctrl_1 |= LLC_2_PDU_RSP_UA;
  	pdu->ctrl_1 |= ((f_bit & 1) << 4) & LLC_U_PF_BIT_MASK;
  }
  
  /**
   *	llc_pdu_decode_pdu_type - designates PDU type
   *	@skb: input skb that type of it must be designated.
   *	@type: type of PDU (output argument).
   *
   *	This function designates type of PDU (I, S or U).
   */
  static void llc_pdu_decode_pdu_type(struct sk_buff *skb, u8 *type)
  {
  	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
  
  	if (pdu->ctrl_1 & 1) {
  		if ((pdu->ctrl_1 & LLC_PDU_TYPE_U) == LLC_PDU_TYPE_U)
  			*type = LLC_PDU_TYPE_U;
  		else
  			*type = LLC_PDU_TYPE_S;
  	} else
  		*type = LLC_PDU_TYPE_I;
  }
  
  /**
   *	llc_pdu_get_pf_bit - extracts p/f bit of input PDU
   *	@pdu: pointer to LLC header.
   *
   *	This function extracts p/f bit of input PDU. at first examines type of
   *	PDU and then extracts p/f bit. Returns the p/f bit.
   */
  static u8 llc_pdu_get_pf_bit(struct llc_pdu_sn *pdu)
  {
  	u8 pdu_type;
  	u8 pf_bit = 0;
  
  	if (pdu->ctrl_1 & 1) {
  		if ((pdu->ctrl_1 & LLC_PDU_TYPE_U) == LLC_PDU_TYPE_U)
  			pdu_type = LLC_PDU_TYPE_U;
  		else
  			pdu_type = LLC_PDU_TYPE_S;
  	} else
  		pdu_type = LLC_PDU_TYPE_I;
  	switch (pdu_type) {
  	case LLC_PDU_TYPE_I:
  	case LLC_PDU_TYPE_S:
  		pf_bit = pdu->ctrl_2 & LLC_S_PF_BIT_MASK;
  		break;
  	case LLC_PDU_TYPE_U:
  		pf_bit = (pdu->ctrl_1 & LLC_U_PF_BIT_MASK) >> 4;
  		break;
  	}
  	return pf_bit;
  }