linux/net/llc/llc_output.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * llc_output.c - LLC minimal output path
   4 *
   5 * Copyright (c) 1997 by Procom Technology, Inc.
   6 *               2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   7 */
   8
   9#include <linux/if_arp.h>
  10#include <linux/netdevice.h>
  11#include <linux/skbuff.h>
  12#include <linux/export.h>
  13#include <net/llc.h>
  14#include <net/llc_pdu.h>
  15
  16/**
  17 *      llc_mac_hdr_init - fills MAC header fields
  18 *      @skb: Address of the frame to initialize its MAC header
  19 *      @sa: The MAC source address
  20 *      @da: The MAC destination address
  21 *
  22 *      Fills MAC header fields, depending on MAC type. Returns 0, If MAC type
  23 *      is a valid type and initialization completes correctly 1, otherwise.
  24 */
  25int llc_mac_hdr_init(struct sk_buff *skb,
  26                     const unsigned char *sa, const unsigned char *da)
  27{
  28        int rc = -EINVAL;
  29
  30        switch (skb->dev->type) {
  31        case ARPHRD_ETHER:
  32        case ARPHRD_LOOPBACK:
  33                rc = dev_hard_header(skb, skb->dev, ETH_P_802_2, da, sa,
  34                                     skb->len);
  35                if (rc > 0)
  36                        rc = 0;
  37                break;
  38        default:
  39                break;
  40        }
  41        return rc;
  42}
  43
  44/**
  45 *      llc_build_and_send_ui_pkt - unitdata request interface for upper layers
  46 *      @sap: sap to use
  47 *      @skb: packet to send
  48 *      @dmac: destination mac address
  49 *      @dsap: destination sap
  50 *
  51 *      Upper layers calls this function when upper layer wants to send data
  52 *      using connection-less mode communication (UI pdu).
  53 *
  54 *      Accept data frame from network layer to be sent using connection-
  55 *      less mode communication; timeout/retries handled by network layer;
  56 *      package primitive as an event and send to SAP event handler
  57 */
  58int llc_build_and_send_ui_pkt(struct llc_sap *sap, struct sk_buff *skb,
  59                              unsigned char *dmac, unsigned char dsap)
  60{
  61        int rc;
  62        llc_pdu_header_init(skb, LLC_PDU_TYPE_U, sap->laddr.lsap,
  63                            dsap, LLC_PDU_CMD);
  64        llc_pdu_init_as_ui_cmd(skb);
  65        rc = llc_mac_hdr_init(skb, skb->dev->dev_addr, dmac);
  66        if (likely(!rc))
  67                rc = dev_queue_xmit(skb);
  68        else
  69                kfree_skb(skb);
  70        return rc;
  71}
  72
  73EXPORT_SYMBOL(llc_mac_hdr_init);
  74EXPORT_SYMBOL(llc_build_and_send_ui_pkt);
  75