net/decnet/netfilter/dn_rtmsg.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * DECnet       An implementation of the DECnet protocol suite for the LINUX
   4  *              operating system.  DECnet is implemented using the  BSD Socket
   5  *              interface as the means of communication with the user level.
   6  *
   7  *              DECnet Routing Message Grabulator
   8  *
   9  *              (C) 2000 ChyGwyn Limited  -  http://www.chygwyn.com/
  10  *
  11  * Author:      Steven Whitehouse <steve@chygwyn.com>
  12  */
  13 #include <linux/module.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/slab.h>
  16 #include <linux/init.h>
  17 #include <linux/netdevice.h>
  18 #include <linux/netfilter.h>
  19 #include <linux/spinlock.h>
  20 #include <net/netlink.h>
  21 #include <linux/netfilter_decnet.h>
  22
  23 #include <net/sock.h>
  24 #include <net/flow.h>
  25 #include <net/dn.h>
  26 #include <net/dn_route.h>
  27
  28 static struct sock *dnrmg = NULL;
  29
  30
  31 static struct sk_buff *dnrmg_build_message(struct sk_buff *rt_skb, int *errp)
  32 {
  33         struct sk_buff *skb = NULL;
  34         size_t size;
  35         sk_buff_data_t old_tail;
  36         struct nlmsghdr *nlh;
  37         unsigned char *ptr;
  38         struct nf_dn_rtmsg *rtm;
  39
  40         size = NLMSG_ALIGN(rt_skb->len) +
  41                NLMSG_ALIGN(sizeof(struct nf_dn_rtmsg));
  42         skb = nlmsg_new(size, GFP_ATOMIC);
  43         if (!skb) {
  44                 *errp = -ENOMEM;
  45                 return NULL;
  46         }
  47         old_tail = skb->tail;
  48         nlh = nlmsg_put(skb, 0, 0, 0, size, 0);
  49         if (!nlh) {
  50                 kfree_skb(skb);
  51                 *errp = -ENOMEM;
  52                 return NULL;
  53         }
  54         rtm = (struct nf_dn_rtmsg *)nlmsg_data(nlh);
  55         rtm->nfdn_ifindex = rt_skb->dev->ifindex;
  56         ptr = NFDN_RTMSG(rtm);
  57         skb_copy_from_linear_data(rt_skb, ptr, rt_skb->len);
  58         nlh->nlmsg_len = skb->tail - old_tail;
  59         return skb;
  60 }
  61
  62 static void dnrmg_send_peer(struct sk_buff *skb)
  63 {
  64         struct sk_buff *skb2;
  65         int status = 0;
  66         int group = 0;
  67         unsigned char flags = *skb->data;
  68
  69         switch (flags & DN_RT_CNTL_MSK) {
  70         case DN_RT_PKT_L1RT:
  71                 group = DNRNG_NLGRP_L1;
  72                 break;
  73         case DN_RT_PKT_L2RT:
  74                 group = DNRNG_NLGRP_L2;
  75                 break;
  76         default:
  77                 return;
  78         }
  79
  80         skb2 = dnrmg_build_message(skb, &status);
  81         if (skb2 == NULL)
  82                 return;
  83         NETLINK_CB(skb2).dst_group = group;
  84         netlink_broadcast(dnrmg, skb2, 0, group, GFP_ATOMIC);
  85 }
  86
  87
  88 static unsigned int dnrmg_hook(void *priv,
  89                         struct sk_buff *skb,
  90                         const struct nf_hook_state *state)
  91 {
  92         dnrmg_send_peer(skb);
  93         return NF_ACCEPT;
  94 }
  95
  96
  97 #define RCV_SKB_FAIL(err) do { netlink_ack(skb, nlh, (err), NULL); return; } while (0)
  98
  99 static inline void dnrmg_receive_user_skb(struct sk_buff *skb)
 100 {
 101         struct nlmsghdr *nlh = nlmsg_hdr(skb);
 102
 103         if (skb->len < sizeof(*nlh) ||
 104             nlh->nlmsg_len < sizeof(*nlh) ||
 105             skb->len < nlh->nlmsg_len)
 106                 return;
 107
 108         if (!netlink_capable(skb, CAP_NET_ADMIN))
 109                 RCV_SKB_FAIL(-EPERM);
 110
 111         /* Eventually we might send routing messages too */
 112
 113         RCV_SKB_FAIL(-EINVAL);
 114 }
 115
 116 static const struct nf_hook_ops dnrmg_ops = {
 117         .hook           = dnrmg_hook,
 118         .pf             = NFPROTO_DECNET,
 119         .hooknum        = NF_DN_ROUTE,
 120         .priority       = NF_DN_PRI_DNRTMSG,
 121 };
 122
 123 static int __init dn_rtmsg_init(void)
 124 {
 125         int rv = 0;
 126         struct netlink_kernel_cfg cfg = {
 127                 .groups = DNRNG_NLGRP_MAX,
 128                 .input  = dnrmg_receive_user_skb,
 129         };
 130
 131         dnrmg = netlink_kernel_create(&init_net, NETLINK_DNRTMSG, &cfg);
 132         if (dnrmg == NULL) {
 133                 printk(KERN_ERR "dn_rtmsg: Cannot create netlink socket");
 134                 return -ENOMEM;
 135         }
 136
 137         rv = nf_register_net_hook(&init_net, &dnrmg_ops);
 138         if (rv) {
 139                 netlink_kernel_release(dnrmg);
 140         }
 141
 142         return rv;
 143 }
 144
 145 static void __exit dn_rtmsg_fini(void)
 146 {
 147         nf_unregister_net_hook(&init_net, &dnrmg_ops);
 148         netlink_kernel_release(dnrmg);
 149 }
 150
 151
 152 MODULE_DESCRIPTION("DECnet Routing Message Grabulator");
 153 MODULE_AUTHOR("Steven Whitehouse <steve@chygwyn.com>");
 154 MODULE_LICENSE("GPL");
 155 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_DNRTMSG);
 156
 157 module_init(dn_rtmsg_init);
 158 module_exit(dn_rtmsg_fini);