1 /* 2 * X.25 Packet Layer release 002 3 * 4 * This is ALPHA test software. This code may break your machine, randomly fail to work with new 5 * releases, misbehave and/or generally screw up. It might even work. 6 * 7 * This code REQUIRES 2.1.15 or higher 8 * 9 * This module: 10 * This module is free software; you can redistribute it and/or 11 * modify it under the terms of the GNU General Public License 12 * as published by the Free Software Foundation; either version 13 * 2 of the License, or (at your option) any later version. 14 * 15 * History 16 * X.25 001 Jonathan Naylor Started coding. 17 * 2000-09-04 Henner Eisen Prevent freeing a dangling skb. 18 */ 19 20 #define pr_fmt(fmt) "X25: " fmt 21 22 #include <linux/kernel.h> 23 #include <linux/netdevice.h> 24 #include <linux/skbuff.h> 25 #include <linux/slab.h> 26 #include <net/sock.h> 27 #include <linux/if_arp.h> 28 #include <net/x25.h> 29 #include <net/x25device.h> 30 31 static int x25_receive_data(struct sk_buff *skb, struct x25_neigh *nb) 32 { 33 struct sock *sk; 34 unsigned short frametype; 35 unsigned int lci; 36 37 if (!pskb_may_pull(skb, X25_STD_MIN_LEN)) 38 return 0; 39 40 frametype = skb->data[2]; 41 lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF); 42 43 /* 44 * LCI of zero is always for us, and its always a link control 45 * frame. 46 */ 47 if (lci == 0) { 48 x25_link_control(skb, nb, frametype); 49 return 0; 50 } 51 52 /* 53 * Find an existing socket. 54 */ 55 if ((sk = x25_find_socket(lci, nb)) != NULL) { 56 int queued = 1; 57 58 skb_reset_transport_header(skb); 59 bh_lock_sock(sk); 60 if (!sock_owned_by_user(sk)) { 61 queued = x25_process_rx_frame(sk, skb); 62 } else { 63 queued = !sk_add_backlog(sk, skb, sk->sk_rcvbuf); 64 } 65 bh_unlock_sock(sk); 66 sock_put(sk); 67 return queued; 68 } 69 70 /* 71 * Is is a Call Request ? if so process it. 72 */ 73 if (frametype == X25_CALL_REQUEST) 74 return x25_rx_call_request(skb, nb, lci); 75 76 /* 77 * Its not a Call Request, nor is it a control frame. 78 * Can we forward it? 79 */ 80 81 if (x25_forward_data(lci, nb, skb)) { 82 if (frametype == X25_CLEAR_CONFIRMATION) { 83 x25_clear_forward_by_lci(lci); 84 } 85 kfree_skb(skb); 86 return 1; 87 } 88 89 /* 90 x25_transmit_clear_request(nb, lci, 0x0D); 91 */ 92 93 if (frametype != X25_CLEAR_CONFIRMATION) 94 pr_debug("x25_receive_data(): unknown frame type %2x\n",frametype); 95 96 return 0; 97 } 98 99 int x25_lapb_receive_frame(struct sk_buff *skb, struct net_device *dev, 100 struct packet_type *ptype, struct net_device *orig_dev) 101 { 102 struct sk_buff *nskb; 103 struct x25_neigh *nb; 104 105 if (!net_eq(dev_net(dev), &init_net)) 106 goto drop; 107 108 nskb = skb_copy(skb, GFP_ATOMIC); 109 if (!nskb) 110 goto drop; 111 kfree_skb(skb); 112 skb = nskb; 113 114 /* 115 * Packet received from unrecognised device, throw it away. 116 */ 117 nb = x25_get_neigh(dev); 118 if (!nb) { 119 pr_debug("unknown neighbour - %s\n", dev->name); 120 goto drop; 121 } 122 123 if (!pskb_may_pull(skb, 1)) 124 return 0; 125 126 switch (skb->data[0]) { 127 128 case X25_IFACE_DATA: 129 skb_pull(skb, 1); 130 if (x25_receive_data(skb, nb)) { 131 x25_neigh_put(nb); 132 goto out; 133 } 134 break; 135 136 case X25_IFACE_CONNECT: 137 x25_link_established(nb); 138 break; 139 140 case X25_IFACE_DISCONNECT: 141 x25_link_terminated(nb); 142 break; 143 } 144 x25_neigh_put(nb); 145 drop: 146 kfree_skb(skb); 147 out: 148 return 0; 149 } 150 151 void x25_establish_link(struct x25_neigh *nb) 152 { 153 struct sk_buff *skb; 154 unsigned char *ptr; 155 156 switch (nb->dev->type) { 157 case ARPHRD_X25: 158 if ((skb = alloc_skb(1, GFP_ATOMIC)) == NULL) { 159 pr_err("x25_dev: out of memory\n"); 160 return; 161 } 162 ptr = skb_put(skb, 1); 163 *ptr = X25_IFACE_CONNECT; 164 break; 165 166 #if IS_ENABLED(CONFIG_LLC) 167 case ARPHRD_ETHER: 168 return; 169 #endif 170 default: 171 return; 172 } 173 174 skb->protocol = htons(ETH_P_X25); 175 skb->dev = nb->dev; 176 177 dev_queue_xmit(skb); 178 } 179 180 void x25_terminate_link(struct x25_neigh *nb) 181 { 182 struct sk_buff *skb; 183 unsigned char *ptr; 184 185 #if IS_ENABLED(CONFIG_LLC) 186 if (nb->dev->type == ARPHRD_ETHER) 187 return; 188 #endif 189 if (nb->dev->type != ARPHRD_X25) 190 return; 191 192 skb = alloc_skb(1, GFP_ATOMIC); 193 if (!skb) { 194 pr_err("x25_dev: out of memory\n"); 195 return; 196 } 197 198 ptr = skb_put(skb, 1); 199 *ptr = X25_IFACE_DISCONNECT; 200 201 skb->protocol = htons(ETH_P_X25); 202 skb->dev = nb->dev; 203 dev_queue_xmit(skb); 204 } 205 206 void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb) 207 { 208 unsigned char *dptr; 209 210 skb_reset_network_header(skb); 211 212 switch (nb->dev->type) { 213 case ARPHRD_X25: 214 dptr = skb_push(skb, 1); 215 *dptr = X25_IFACE_DATA; 216 break; 217 218 #if IS_ENABLED(CONFIG_LLC) 219 case ARPHRD_ETHER: 220 kfree_skb(skb); 221 return; 222 #endif 223 default: 224 kfree_skb(skb); 225 return; 226 } 227 228 skb->protocol = htons(ETH_P_X25); 229 skb->dev = nb->dev; 230 231 dev_queue_xmit(skb); 232 } 233