net/wan/hdlc.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Generic HDLC support routines for Linux
0004  *
0005  * Copyright (C) 1999 - 2008 Krzysztof Halasa <khc@pm.waw.pl>
0006  *
0007  * Currently supported:
0008  *  * raw IP-in-HDLC
0009  *  * Cisco HDLC
0010  *  * Frame Relay with ANSI or CCITT LMI (both user and network side)
0011  *  * PPP
0012  *  * X.25
0013  *
0014  * Use sethdlc utility to set line parameters, protocol and PVCs
0015  *
0016  * How does it work:
0017  * - proto->open(), close(), start(), stop() calls are serialized.
0018  *   The order is: open, [ start, stop ... ] close ...
0019  * - proto->start() and stop() are called with spin_lock_irq held.
0020  */
0021
0022 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0023
0024 #include <linux/errno.h>
0025 #include <linux/hdlc.h>
0026 #include <linux/if_arp.h>
0027 #include <linux/inetdevice.h>
0028 #include <linux/init.h>
0029 #include <linux/kernel.h>
0030 #include <linux/module.h>
0031 #include <linux/notifier.h>
0032 #include <linux/pkt_sched.h>
0033 #include <linux/poll.h>
0034 #include <linux/rtnetlink.h>
0035 #include <linux/skbuff.h>
0036 #include <linux/slab.h>
0037 #include <net/net_namespace.h>
0038
0039 static const char *version = "HDLC support module revision 1.22";
0040
0041 #undef DEBUG_LINK
0042
0043 static struct hdlc_proto *first_proto;
0044
0045 static int hdlc_rcv(struct sk_buff *skb, struct net_device *dev,
0046             struct packet_type *p, struct net_device *orig_dev)
0047 {
0048     struct hdlc_device *hdlc;
0049
0050     /* First make sure "dev" is an HDLC device */
0051     if (!(dev->priv_flags & IFF_WAN_HDLC)) {
0052         kfree_skb(skb);
0053         return NET_RX_SUCCESS;
0054     }
0055
0056     hdlc = dev_to_hdlc(dev);
0057
0058     if (!net_eq(dev_net(dev), &init_net)) {
0059         kfree_skb(skb);
0060         return 0;
0061     }
0062
0063     BUG_ON(!hdlc->proto->netif_rx);
0064     return hdlc->proto->netif_rx(skb);
0065 }
0066
0067 netdev_tx_t hdlc_start_xmit(struct sk_buff *skb, struct net_device *dev)
0068 {
0069     hdlc_device *hdlc = dev_to_hdlc(dev);
0070
0071     if (hdlc->proto->xmit)
0072         return hdlc->proto->xmit(skb, dev);
0073
0074     return hdlc->xmit(skb, dev); /* call hardware driver directly */
0075 }
0076 EXPORT_SYMBOL(hdlc_start_xmit);
0077
0078 static inline void hdlc_proto_start(struct net_device *dev)
0079 {
0080     hdlc_device *hdlc = dev_to_hdlc(dev);
0081
0082     if (hdlc->proto->start)
0083         hdlc->proto->start(dev);
0084 }
0085
0086 static inline void hdlc_proto_stop(struct net_device *dev)
0087 {
0088     hdlc_device *hdlc = dev_to_hdlc(dev);
0089
0090     if (hdlc->proto->stop)
0091         hdlc->proto->stop(dev);
0092 }
0093
0094 static int hdlc_device_event(struct notifier_block *this, unsigned long event,
0095                  void *ptr)
0096 {
0097     struct net_device *dev = netdev_notifier_info_to_dev(ptr);
0098     hdlc_device *hdlc;
0099     unsigned long flags;
0100     int on;
0101
0102     if (!net_eq(dev_net(dev), &init_net))
0103         return NOTIFY_DONE;
0104
0105     if (!(dev->priv_flags & IFF_WAN_HDLC))
0106         return NOTIFY_DONE; /* not an HDLC device */
0107
0108     if (event != NETDEV_CHANGE)
0109         return NOTIFY_DONE; /* Only interested in carrier changes */
0110
0111     on = netif_carrier_ok(dev);
0112
0113 #ifdef DEBUG_LINK
0114     printk(KERN_DEBUG "%s: hdlc_device_event NETDEV_CHANGE, carrier %i\n",
0115            dev->name, on);
0116 #endif
0117
0118     hdlc = dev_to_hdlc(dev);
0119     spin_lock_irqsave(&hdlc->state_lock, flags);
0120
0121     if (hdlc->carrier == on)
0122         goto carrier_exit; /* no change in DCD line level */
0123
0124     hdlc->carrier = on;
0125
0126     if (!hdlc->open)
0127         goto carrier_exit;
0128
0129     if (hdlc->carrier) {
0130         netdev_info(dev, "Carrier detected\n");
0131         hdlc_proto_start(dev);
0132     } else {
0133         netdev_info(dev, "Carrier lost\n");
0134         hdlc_proto_stop(dev);
0135     }
0136
0137 carrier_exit:
0138     spin_unlock_irqrestore(&hdlc->state_lock, flags);
0139     return NOTIFY_DONE;
0140 }
0141
0142 /* Must be called by hardware driver when HDLC device is being opened */
0143 int hdlc_open(struct net_device *dev)
0144 {
0145     hdlc_device *hdlc = dev_to_hdlc(dev);
0146 #ifdef DEBUG_LINK
0147     printk(KERN_DEBUG "%s: hdlc_open() carrier %i open %i\n", dev->name,
0148            hdlc->carrier, hdlc->open);
0149 #endif
0150
0151     if (!hdlc->proto)
0152         return -ENOSYS; /* no protocol attached */
0153
0154     if (hdlc->proto->open) {
0155         int result = hdlc->proto->open(dev);
0156
0157         if (result)
0158             return result;
0159     }
0160
0161     spin_lock_irq(&hdlc->state_lock);
0162
0163     if (hdlc->carrier) {
0164         netdev_info(dev, "Carrier detected\n");
0165         hdlc_proto_start(dev);
0166     } else {
0167         netdev_info(dev, "No carrier\n");
0168     }
0169
0170     hdlc->open = 1;
0171
0172     spin_unlock_irq(&hdlc->state_lock);
0173     return 0;
0174 }
0175 EXPORT_SYMBOL(hdlc_open);
0176
0177 /* Must be called by hardware driver when HDLC device is being closed */
0178 void hdlc_close(struct net_device *dev)
0179 {
0180     hdlc_device *hdlc = dev_to_hdlc(dev);
0181 #ifdef DEBUG_LINK
0182     printk(KERN_DEBUG "%s: hdlc_close() carrier %i open %i\n", dev->name,
0183            hdlc->carrier, hdlc->open);
0184 #endif
0185
0186     spin_lock_irq(&hdlc->state_lock);
0187
0188     hdlc->open = 0;
0189     if (hdlc->carrier)
0190         hdlc_proto_stop(dev);
0191
0192     spin_unlock_irq(&hdlc->state_lock);
0193
0194     if (hdlc->proto->close)
0195         hdlc->proto->close(dev);
0196 }
0197 EXPORT_SYMBOL(hdlc_close);
0198
0199 int hdlc_ioctl(struct net_device *dev, struct if_settings *ifs)
0200 {
0201     struct hdlc_proto *proto = first_proto;
0202     int result;
0203
0204     if (dev_to_hdlc(dev)->proto) {
0205         result = dev_to_hdlc(dev)->proto->ioctl(dev, ifs);
0206         if (result != -EINVAL)
0207             return result;
0208     }
0209
0210     /* Not handled by currently attached protocol (if any) */
0211
0212     while (proto) {
0213         result = proto->ioctl(dev, ifs);
0214         if (result != -EINVAL)
0215             return result;
0216         proto = proto->next;
0217     }
0218     return -EINVAL;
0219 }
0220 EXPORT_SYMBOL(hdlc_ioctl);
0221
0222 static const struct header_ops hdlc_null_ops;
0223
0224 static void hdlc_setup_dev(struct net_device *dev)
0225 {
0226     /* Re-init all variables changed by HDLC protocol drivers,
0227      * including ether_setup() called from hdlc_raw_eth.c.
0228      */
0229     dev->flags       = IFF_POINTOPOINT | IFF_NOARP;
0230     dev->priv_flags      = IFF_WAN_HDLC;
0231     dev->mtu         = HDLC_MAX_MTU;
0232     dev->min_mtu         = 68;
0233     dev->max_mtu         = HDLC_MAX_MTU;
0234     dev->type        = ARPHRD_RAWHDLC;
0235     dev->hard_header_len     = 0;
0236     dev->needed_headroom     = 0;
0237     dev->addr_len        = 0;
0238     dev->header_ops      = &hdlc_null_ops;
0239 }
0240
0241 static void hdlc_setup(struct net_device *dev)
0242 {
0243     hdlc_device *hdlc = dev_to_hdlc(dev);
0244
0245     hdlc_setup_dev(dev);
0246     hdlc->carrier = 1;
0247     hdlc->open = 0;
0248     spin_lock_init(&hdlc->state_lock);
0249 }
0250
0251 struct net_device *alloc_hdlcdev(void *priv)
0252 {
0253     struct net_device *dev;
0254
0255     dev = alloc_netdev(sizeof(struct hdlc_device), "hdlc%d",
0256                NET_NAME_UNKNOWN, hdlc_setup);
0257     if (dev)
0258         dev_to_hdlc(dev)->priv = priv;
0259     return dev;
0260 }
0261 EXPORT_SYMBOL(alloc_hdlcdev);
0262
0263 void unregister_hdlc_device(struct net_device *dev)
0264 {
0265     rtnl_lock();
0266     detach_hdlc_protocol(dev);
0267     unregister_netdevice(dev);
0268     rtnl_unlock();
0269 }
0270 EXPORT_SYMBOL(unregister_hdlc_device);
0271
0272 int attach_hdlc_protocol(struct net_device *dev, struct hdlc_proto *proto,
0273              size_t size)
0274 {
0275     int err;
0276
0277     err = detach_hdlc_protocol(dev);
0278     if (err)
0279         return err;
0280
0281     if (!try_module_get(proto->module))
0282         return -ENOSYS;
0283
0284     if (size) {
0285         dev_to_hdlc(dev)->state = kmalloc(size, GFP_KERNEL);
0286         if (!dev_to_hdlc(dev)->state) {
0287             module_put(proto->module);
0288             return -ENOBUFS;
0289         }
0290     }
0291     dev_to_hdlc(dev)->proto = proto;
0292
0293     return 0;
0294 }
0295 EXPORT_SYMBOL(attach_hdlc_protocol);
0296
0297 int detach_hdlc_protocol(struct net_device *dev)
0298 {
0299     hdlc_device *hdlc = dev_to_hdlc(dev);
0300     int err;
0301
0302     if (hdlc->proto) {
0303         err = call_netdevice_notifiers(NETDEV_PRE_TYPE_CHANGE, dev);
0304         err = notifier_to_errno(err);
0305         if (err) {
0306             netdev_err(dev, "Refused to change device type\n");
0307             return err;
0308         }
0309
0310         if (hdlc->proto->detach)
0311             hdlc->proto->detach(dev);
0312         module_put(hdlc->proto->module);
0313         hdlc->proto = NULL;
0314     }
0315     kfree(hdlc->state);
0316     hdlc->state = NULL;
0317     hdlc_setup_dev(dev);
0318
0319     return 0;
0320 }
0321 EXPORT_SYMBOL(detach_hdlc_protocol);
0322
0323 void register_hdlc_protocol(struct hdlc_proto *proto)
0324 {
0325     rtnl_lock();
0326     proto->next = first_proto;
0327     first_proto = proto;
0328     rtnl_unlock();
0329 }
0330 EXPORT_SYMBOL(register_hdlc_protocol);
0331
0332 void unregister_hdlc_protocol(struct hdlc_proto *proto)
0333 {
0334     struct hdlc_proto **p;
0335
0336     rtnl_lock();
0337     p = &first_proto;
0338     while (*p != proto) {
0339         BUG_ON(!*p);
0340         p = &((*p)->next);
0341     }
0342     *p = proto->next;
0343     rtnl_unlock();
0344 }
0345 EXPORT_SYMBOL(unregister_hdlc_protocol);
0346
0347 MODULE_AUTHOR("Krzysztof Halasa <khc@pm.waw.pl>");
0348 MODULE_DESCRIPTION("HDLC support module");
0349 MODULE_LICENSE("GPL v2");
0350
0351 static struct packet_type hdlc_packet_type __read_mostly = {
0352     .type = cpu_to_be16(ETH_P_HDLC),
0353     .func = hdlc_rcv,
0354 };
0355
0356 static struct notifier_block hdlc_notifier = {
0357     .notifier_call = hdlc_device_event,
0358 };
0359
0360 static int __init hdlc_module_init(void)
0361 {
0362     int result;
0363
0364     pr_info("%s\n", version);
0365     result = register_netdevice_notifier(&hdlc_notifier);
0366     if (result)
0367         return result;
0368     dev_add_pack(&hdlc_packet_type);
0369     return 0;
0370 }
0371
0372 static void __exit hdlc_module_exit(void)
0373 {
0374     dev_remove_pack(&hdlc_packet_type);
0375     unregister_netdevice_notifier(&hdlc_notifier);
0376 }
0377
0378 module_init(hdlc_module_init);
0379 module_exit(hdlc_module_exit);