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         if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) {
 126                 kfree_skb(skb);
 127                 goto put;
 128         }
 129
 130         if (bp[16] == AX25_P_IP) {
 131                 if (ip_mode == 'V' || (ip_mode == ' ' && ax25_dev->values[AX25_VALUES_IPDEFMODE])) {
 132                         /*
 133                          *      We copy the buffer and release the original thereby
 134                          *      keeping it straight
 135                          *
 136                          *      Note: we report 1 back so the caller will
 137                          *      not feed the frame direct to the physical device
 138                          *      We don't want that to happen. (It won't be upset
 139                          *      as we have pulled the frame from the queue by
 140                          *      freeing it).
 141                          *
 142                          *      NB: TCP modifies buffers that are still
 143                          *      on a device queue, thus we use skb_copy()
 144                          *      instead of using skb_clone() unless this
 145                          *      gets fixed.
 146                          */
 147
 148                         ax25_address src_c;
 149                         ax25_address dst_c;
 150
 151                         if ((ourskb = skb_copy(skb, GFP_ATOMIC)) == NULL) {
 152                                 kfree_skb(skb);
 153                                 goto put;
 154                         }
 155
 156                         if (skb->sk != NULL)
 157                                 skb_set_owner_w(ourskb, skb->sk);
 158
 159                         kfree_skb(skb);
 160                         /* dl9sau: bugfix
 161                          * after kfree_skb(), dst and src which were pointer
 162                          * to bp which is part of skb->data would not be valid
 163                          * anymore hope that after skb_pull(ourskb, ..) our
 164                          * dsc_c and src_c will not become invalid
 165                          */
 166                         bp  = ourskb->data;
 167                         dst_c = *(ax25_address *)(bp + 1);
 168                         src_c = *(ax25_address *)(bp + 8);
 169
 170                         skb_pull(ourskb, AX25_HEADER_LEN - 1);  /* Keep PID */
 171                         skb_reset_network_header(ourskb);
 172
 173                         ax25=ax25_send_frame(
 174                             ourskb,
 175                             ax25_dev->values[AX25_VALUES_PACLEN],
 176                             &src_c,
 177                             &dst_c, digipeat, dev);
 178                         if (ax25) {
 179                                 ax25_cb_put(ax25);
 180                         }
 181                         goto put;
 182                 }
 183         }
 184
 185         bp[7]  &= ~AX25_CBIT;
 186         bp[7]  &= ~AX25_EBIT;
 187         bp[7]  |= AX25_SSSID_SPARE;
 188
 189         bp[14] &= ~AX25_CBIT;
 190         bp[14] |= AX25_EBIT;
 191         bp[14] |= AX25_SSSID_SPARE;
 192
 193         skb_pull(skb, AX25_KISS_HEADER_LEN);
 194
 195         if (digipeat != NULL) {
 196                 if ((ourskb = ax25_rt_build_path(skb, src, dst, route->digipeat)) == NULL)
 197                         goto put;
 198
 199                 skb = ourskb;
 200         }
 201
 202         ax25_queue_xmit(skb, dev);
 203
 204 put:
 205
 206         ax25_route_lock_unuse();
 207         return NETDEV_TX_OK;
 208 }
 209
 210 #else   /* INET */
 211
 212 static int ax25_hard_header(struct sk_buff *skb, struct net_device *dev,
 213                             unsigned short type, const void *daddr,
 214                             const void *saddr, unsigned int len)
 215 {
 216         return -AX25_HEADER_LEN;
 217 }
 218
 219 netdev_tx_t ax25_ip_xmit(struct sk_buff *skb)
 220 {
 221         kfree_skb(skb);
 222         return NETDEV_TX_OK;
 223 }
 224 #endif
 225
 226 static bool ax25_validate_header(const char *header, unsigned int len)
 227 {
 228         ax25_digi digi;
 229
 230         if (!len)
 231                 return false;
 232
 233         if (header[0])
 234                 return true;
 235
 236         return ax25_addr_parse(header + 1, len - 1, NULL, NULL, &digi, NULL,
 237                                NULL);
 238 }
 239
 240 const struct header_ops ax25_header_ops = {
 241         .create = ax25_hard_header,
 242         .validate = ax25_validate_header,
 243 };
 244
 245 EXPORT_SYMBOL(ax25_header_ops);
 246 EXPORT_SYMBOL(ax25_ip_xmit);