net/ax25/ax25_ip.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *
   4  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   5  */
   6 #include <linux/errno.h>
   7 #include <linux/types.h>
   8 #include <linux/socket.h>
   9 #include <linux/in.h>
  10 #include <linux/kernel.h>
  11 #include <linux/module.h>
  12 #include <linux/timer.h>
  13 #include <linux/string.h>
  14 #include <linux/sockios.h>
  15 #include <linux/net.h>
  16 #include <linux/slab.h>
  17 #include <net/ax25.h>
  18 #include <linux/inet.h>
  19 #include <linux/netdevice.h>
  20 #include <linux/if_arp.h>
  21 #include <linux/skbuff.h>
  22 #include <net/sock.h>
  23 #include <linux/uaccess.h>
  24 #include <linux/fcntl.h>
  25 #include <linux/termios.h>      /* For TIOCINQ/OUTQ */
  26 #include <linux/mm.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/notifier.h>
  29 #include <linux/proc_fs.h>
  30 #include <linux/stat.h>
  31 #include <linux/sysctl.h>
  32 #include <net/ip.h>
  33 #include <net/arp.h>
  34
  35 /*
  36  *      IP over AX.25 encapsulation.
  37  */
  38
  39 /*
  40  *      Shove an AX.25 UI header on an IP packet and handle ARP
  41  */
  42
  43 #ifdef CONFIG_INET
  44
  45 static int ax25_hard_header(struct sk_buff *skb, struct net_device *dev,
  46                             unsigned short type, const void *daddr,
  47                             const void *saddr, unsigned int len)
  48 {
  49         unsigned char *buff;
  50
  51         /* they sometimes come back to us... */
  52         if (type == ETH_P_AX25)
  53                 return 0;
  54
  55         /* header is an AX.25 UI frame from us to them */
  56         buff = skb_push(skb, AX25_HEADER_LEN);
  57         *buff++ = 0x00; /* KISS DATA */
  58
  59         if (daddr != NULL)
  60                 memcpy(buff, daddr, dev->addr_len);     /* Address specified */
  61
  62         buff[6] &= ~AX25_CBIT;
  63         buff[6] &= ~AX25_EBIT;
  64         buff[6] |= AX25_SSSID_SPARE;
  65         buff    += AX25_ADDR_LEN;
  66
  67         if (saddr != NULL)
  68                 memcpy(buff, saddr, dev->addr_len);
  69         else
  70                 memcpy(buff, dev->dev_addr, dev->addr_len);
  71
  72         buff[6] &= ~AX25_CBIT;
  73         buff[6] |= AX25_EBIT;
  74         buff[6] |= AX25_SSSID_SPARE;
  75         buff    += AX25_ADDR_LEN;
  76
  77         *buff++  = AX25_UI;     /* UI */
  78
  79         /* Append a suitable AX.25 PID */
  80         switch (type) {
  81         case ETH_P_IP:
  82                 *buff++ = AX25_P_IP;
  83                 break;
  84         case ETH_P_ARP:
  85                 *buff++ = AX25_P_ARP;
  86                 break;
  87         default:
  88                 printk(KERN_ERR "AX.25: ax25_hard_header - wrong protocol type 0x%2.2x\n", type);
  89                 *buff++ = 0;
  90                 break;
  91         }
  92
  93         if (daddr != NULL)
  94                 return AX25_HEADER_LEN;
  95
  96         return -AX25_HEADER_LEN;        /* Unfinished header */
  97 }
  98
  99 netdev_tx_t ax25_ip_xmit(struct sk_buff *skb)
 100 {
 101         struct sk_buff *ourskb;
 102         unsigned char *bp  = skb->data;
 103         ax25_route *route;
 104         struct net_device *dev = NULL;
 105         ax25_address *src, *dst;
 106         ax25_digi *digipeat = NULL;
 107         ax25_dev *ax25_dev;
 108         ax25_cb *ax25;
 109         char ip_mode = ' ';
 110
 111         dst = (ax25_address *)(bp + 1);
 112         src = (ax25_address *)(bp + 8);
 113
 114         ax25_route_lock_use();
 115         route = ax25_get_route(dst, NULL);
 116         if (route) {
 117                 digipeat = route->digipeat;
 118                 dev = route->dev;
 119                 ip_mode = route->ip_mode;
 120         }
 121
 122         if (dev == NULL)
 123                 dev = skb->dev;
 124
 125         rcu_read_lock();
 126         if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) {
 127                 kfree_skb(skb);
 128                 goto put;
 129         }
 130
 131         if (bp[16] == AX25_P_IP) {
 132                 if (ip_mode == 'V' || (ip_mode == ' ' && ax25_dev->values[AX25_VALUES_IPDEFMODE])) {
 133                         /*
 134                          *      We copy the buffer and release the original thereby
 135                          *      keeping it straight
 136                          *
 137                          *      Note: we report 1 back so the caller will
 138                          *      not feed the frame direct to the physical device
 139                          *      We don't want that to happen. (It won't be upset
 140                          *      as we have pulled the frame from the queue by
 141                          *      freeing it).
 142                          *
 143                          *      NB: TCP modifies buffers that are still
 144                          *      on a device queue, thus we use skb_copy()
 145                          *      instead of using skb_clone() unless this
 146                          *      gets fixed.
 147                          */
 148
 149                         ax25_address src_c;
 150                         ax25_address dst_c;
 151
 152                         if ((ourskb = skb_copy(skb, GFP_ATOMIC)) == NULL) {
 153                                 kfree_skb(skb);
 154                                 goto put;
 155                         }
 156
 157                         if (skb->sk != NULL)
 158                                 skb_set_owner_w(ourskb, skb->sk);
 159
 160                         kfree_skb(skb);
 161                         /* dl9sau: bugfix
 162                          * after kfree_skb(), dst and src which were pointer
 163                          * to bp which is part of skb->data would not be valid
 164                          * anymore hope that after skb_pull(ourskb, ..) our
 165                          * dsc_c and src_c will not become invalid
 166                          */
 167                         bp  = ourskb->data;
 168                         dst_c = *(ax25_address *)(bp + 1);
 169                         src_c = *(ax25_address *)(bp + 8);
 170
 171                         skb_pull(ourskb, AX25_HEADER_LEN - 1);  /* Keep PID */
 172                         skb_reset_network_header(ourskb);
 173
 174                         ax25=ax25_send_frame(
 175                             ourskb,
 176                             ax25_dev->values[AX25_VALUES_PACLEN],
 177                             &src_c,
 178                             &dst_c, digipeat, dev);
 179                         if (ax25) {
 180                                 ax25_cb_put(ax25);
 181                         }
 182                         goto put;
 183                 }
 184         }
 185
 186         bp[7]  &= ~AX25_CBIT;
 187         bp[7]  &= ~AX25_EBIT;
 188         bp[7]  |= AX25_SSSID_SPARE;
 189
 190         bp[14] &= ~AX25_CBIT;
 191         bp[14] |= AX25_EBIT;
 192         bp[14] |= AX25_SSSID_SPARE;
 193
 194         skb_pull(skb, AX25_KISS_HEADER_LEN);
 195
 196         if (digipeat != NULL) {
 197                 if ((ourskb = ax25_rt_build_path(skb, src, dst, route->digipeat)) == NULL)
 198                         goto put;
 199
 200                 skb = ourskb;
 201         }
 202
 203         ax25_queue_xmit(skb, dev);
 204
 205 put:
 206         rcu_read_unlock();
 207         ax25_route_lock_unuse();
 208         return NETDEV_TX_OK;
 209 }
 210
 211 #else   /* INET */
 212
 213 static int ax25_hard_header(struct sk_buff *skb, struct net_device *dev,
 214                             unsigned short type, const void *daddr,
 215                             const void *saddr, unsigned int len)
 216 {
 217         return -AX25_HEADER_LEN;
 218 }
 219
 220 netdev_tx_t ax25_ip_xmit(struct sk_buff *skb)
 221 {
 222         kfree_skb(skb);
 223         return NETDEV_TX_OK;
 224 }
 225 #endif
 226
 227 static bool ax25_validate_header(const char *header, unsigned int len)
 228 {
 229         ax25_digi digi;
 230
 231         if (!len)
 232                 return false;
 233
 234         if (header[0])
 235                 return true;
 236
 237         return ax25_addr_parse(header + 1, len - 1, NULL, NULL, &digi, NULL,
 238                                NULL);
 239 }
 240
 241 const struct header_ops ax25_header_ops = {
 242         .create = ax25_hard_header,
 243         .validate = ax25_validate_header,
 244 };
 245
 246 EXPORT_SYMBOL(ax25_header_ops);
 247 EXPORT_SYMBOL(ax25_ip_xmit);