1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * X.25 Packet Layer release 002 4 * 5 * This is ALPHA test software. This code may break your machine, randomly fail to work with new 6 * releases, misbehave and/or generally screw up. It might even work. 7 * 8 * This code REQUIRES 2.1.15 or higher 9 * 10 * History 11 * X.25 001 Jonathan Naylor Started coding. 12 * 2000-09-04 Henner Eisen Prevent freeing a dangling skb. 13 */ 14 15 #define pr_fmt(fmt) "X25: " fmt 16 17 #include <linux/kernel.h> 18 #include <linux/netdevice.h> 19 #include <linux/skbuff.h> 20 #include <linux/slab.h> 21 #include <net/sock.h> 22 #include <linux/if_arp.h> 23 #include <net/x25.h> 24 #include <net/x25device.h> 25 26 static int x25_receive_data(struct sk_buff *skb, struct x25_neigh *nb) 27 { 28 struct sock *sk; 29 unsigned short frametype; 30 unsigned int lci; 31 32 if (!pskb_may_pull(skb, X25_STD_MIN_LEN)) 33 return 0; 34 35 frametype = skb->data[2]; 36 lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF); 37 38 /* 39 * LCI of zero is always for us, and its always a link control 40 * frame. 41 */ 42 if (lci == 0) { 43 x25_link_control(skb, nb, frametype); 44 return 0; 45 } 46 47 /* 48 * Find an existing socket. 49 */ 50 if ((sk = x25_find_socket(lci, nb)) != NULL) { 51 int queued = 1; 52 53 skb_reset_transport_header(skb); 54 bh_lock_sock(sk); 55 if (!sock_owned_by_user(sk)) { 56 queued = x25_process_rx_frame(sk, skb); 57 } else { 58 queued = !sk_add_backlog(sk, skb, READ_ONCE(sk->sk_rcvbuf)); 59 } 60 bh_unlock_sock(sk); 61 sock_put(sk); 62 return queued; 63 } 64 65 /* 66 * Is is a Call Request ? if so process it. 67 */ 68 if (frametype == X25_CALL_REQUEST) 69 return x25_rx_call_request(skb, nb, lci); 70 71 /* 72 * Its not a Call Request, nor is it a control frame. 73 * Can we forward it? 74 */ 75 76 if (x25_forward_data(lci, nb, skb)) { 77 if (frametype == X25_CLEAR_CONFIRMATION) { 78 x25_clear_forward_by_lci(lci); 79 } 80 kfree_skb(skb); 81 return 1; 82 } 83 84 /* 85 x25_transmit_clear_request(nb, lci, 0x0D); 86 */ 87 88 if (frametype != X25_CLEAR_CONFIRMATION) 89 pr_debug("x25_receive_data(): unknown frame type %2x\n",frametype); 90 91 return 0; 92 } 93 94 int x25_lapb_receive_frame(struct sk_buff *skb, struct net_device *dev, 95 struct packet_type *ptype, struct net_device *orig_dev) 96 { 97 struct sk_buff *nskb; 98 struct x25_neigh *nb; 99 100 if (!net_eq(dev_net(dev), &init_net)) 101 goto drop; 102 103 nskb = skb_copy(skb, GFP_ATOMIC); 104 if (!nskb) 105 goto drop; 106 kfree_skb(skb); 107 skb = nskb; 108 109 /* 110 * Packet received from unrecognised device, throw it away. 111 */ 112 nb = x25_get_neigh(dev); 113 if (!nb) { 114 pr_debug("unknown neighbour - %s\n", dev->name); 115 goto drop; 116 } 117 118 if (!pskb_may_pull(skb, 1)) { 119 x25_neigh_put(nb); 120 goto drop; 121 } 122 123 switch (skb->data[0]) { 124 125 case X25_IFACE_DATA: 126 skb_pull(skb, 1); 127 if (x25_receive_data(skb, nb)) { 128 x25_neigh_put(nb); 129 goto out; 130 } 131 break; 132 133 case X25_IFACE_CONNECT: 134 x25_link_established(nb); 135 break; 136 137 case X25_IFACE_DISCONNECT: 138 x25_link_terminated(nb); 139 break; 140 } 141 x25_neigh_put(nb); 142 drop: 143 kfree_skb(skb); 144 out: 145 return 0; 146 } 147 148 void x25_establish_link(struct x25_neigh *nb) 149 { 150 struct sk_buff *skb; 151 unsigned char *ptr; 152 153 switch (nb->dev->type) { 154 case ARPHRD_X25: 155 if ((skb = alloc_skb(1, GFP_ATOMIC)) == NULL) { 156 pr_err("x25_dev: out of memory\n"); 157 return; 158 } 159 ptr = skb_put(skb, 1); 160 *ptr = X25_IFACE_CONNECT; 161 break; 162 163 default: 164 return; 165 } 166 167 skb->protocol = htons(ETH_P_X25); 168 skb->dev = nb->dev; 169 170 dev_queue_xmit(skb); 171 } 172 173 void x25_terminate_link(struct x25_neigh *nb) 174 { 175 struct sk_buff *skb; 176 unsigned char *ptr; 177 178 if (nb->dev->type != ARPHRD_X25) 179 return; 180 181 skb = alloc_skb(1, GFP_ATOMIC); 182 if (!skb) { 183 pr_err("x25_dev: out of memory\n"); 184 return; 185 } 186 187 ptr = skb_put(skb, 1); 188 *ptr = X25_IFACE_DISCONNECT; 189 190 skb->protocol = htons(ETH_P_X25); 191 skb->dev = nb->dev; 192 dev_queue_xmit(skb); 193 } 194 195 void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb) 196 { 197 unsigned char *dptr; 198 199 skb_reset_network_header(skb); 200 201 switch (nb->dev->type) { 202 case ARPHRD_X25: 203 dptr = skb_push(skb, 1); 204 *dptr = X25_IFACE_DATA; 205 break; 206 207 default: 208 kfree_skb(skb); 209 return; 210 } 211 212 skb->protocol = htons(ETH_P_X25); 213 skb->dev = nb->dev; 214 215 dev_queue_xmit(skb); 216 } 217