/* * GRE over IPv4 demultiplexer driver * * Authors: Dmitry Kozlov (xeb@mail.ru) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/module.h> #include <linux/if.h> #include <linux/icmp.h> #include <linux/kernel.h> #include <linux/kmod.h> #include <linux/skbuff.h> #include <linux/in.h> #include <linux/ip.h> #include <linux/netdevice.h> #include <linux/if_tunnel.h> #include <linux/spinlock.h> #include <net/protocol.h> #include <net/gre.h> #include <net/icmp.h> #include <net/route.h> #include <net/xfrm.h> static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly; static struct gre_cisco_protocol __rcu *gre_cisco_proto_list[GRE_IP_PROTO_MAX]; int gre_add_protocol(const struct gre_protocol *proto, u8 version) { if (version >= GREPROTO_MAX) return -EINVAL; return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ? 0 : -EBUSY; } EXPORT_SYMBOL_GPL(gre_add_protocol); int gre_del_protocol(const struct gre_protocol *proto, u8 version) { int ret; if (version >= GREPROTO_MAX) return -EINVAL; ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ? 0 : -EBUSY; if (ret) return ret; synchronize_rcu(); return 0; } EXPORT_SYMBOL_GPL(gre_del_protocol); void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi, int hdr_len) { struct gre_base_hdr *greh; skb_push(skb, hdr_len); greh = (struct gre_base_hdr *)skb->data; greh->flags = tnl_flags_to_gre_flags(tpi->flags); greh->protocol = tpi->proto; if (tpi->flags&(TUNNEL_KEY|TUNNEL_CSUM|TUNNEL_SEQ)) { __be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4); if (tpi->flags&TUNNEL_SEQ) { *ptr = tpi->seq; ptr--; } if (tpi->flags&TUNNEL_KEY) { *ptr = tpi->key; ptr--; } if (tpi->flags&TUNNEL_CSUM && !(skb_shinfo(skb)->gso_type & SKB_GSO_GRE)) { *ptr = 0; *(__sum16 *)ptr = csum_fold(skb_checksum(skb, 0, skb->len, 0)); } } } EXPORT_SYMBOL_GPL(gre_build_header); struct sk_buff *gre_handle_offloads(struct sk_buff *skb, bool gre_csum) { int err; if (likely(!skb->encapsulation)) { skb_reset_inner_headers(skb); skb->encapsulation = 1; } if (skb_is_gso(skb)) { err = skb_unclone(skb, GFP_ATOMIC); if (unlikely(err)) goto error; skb_shinfo(skb)->gso_type |= SKB_GSO_GRE; return skb; } else if (skb->ip_summed == CHECKSUM_PARTIAL && gre_csum) { err = skb_checksum_help(skb); if (unlikely(err)) goto error; } else if (skb->ip_summed != CHECKSUM_PARTIAL) skb->ip_summed = CHECKSUM_NONE; return skb; error: kfree_skb(skb); return ERR_PTR(err); } EXPORT_SYMBOL_GPL(gre_handle_offloads); static __sum16 check_checksum(struct sk_buff *skb) { __sum16 csum = 0; switch (skb->ip_summed) { case CHECKSUM_COMPLETE: csum = csum_fold(skb->csum); if (!csum) break; /* Fall through. */ case CHECKSUM_NONE: skb->csum = 0; csum = __skb_checksum_complete(skb); skb->ip_summed = CHECKSUM_COMPLETE; break; } return csum; } static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, bool *csum_err) { unsigned int ip_hlen = ip_hdrlen(skb); const struct gre_base_hdr *greh; __be32 *options; int hdr_len; if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr)))) return -EINVAL; greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen); if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING))) return -EINVAL; tpi->flags = gre_flags_to_tnl_flags(greh->flags); hdr_len = ip_gre_calc_hlen(tpi->flags); if (!pskb_may_pull(skb, hdr_len)) return -EINVAL; greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen); tpi->proto = greh->protocol; options = (__be32 *)(greh + 1); if (greh->flags & GRE_CSUM) { if (check_checksum(skb)) { *csum_err = true; return -EINVAL; } options++; } if (greh->flags & GRE_KEY) { tpi->key = *options; options++; } else tpi->key = 0; if (unlikely(greh->flags & GRE_SEQ)) { tpi->seq = *options; options++; } else tpi->seq = 0; /* WCCP version 1 and 2 protocol decoding. * - Change protocol to IP * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header */ if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) { tpi->proto = htons(ETH_P_IP); if ((*(u8 *)options & 0xF0) != 0x40) { hdr_len += 4; if (!pskb_may_pull(skb, hdr_len)) return -EINVAL; } } return iptunnel_pull_header(skb, hdr_len, tpi->proto); } static int gre_cisco_rcv(struct sk_buff *skb) { struct tnl_ptk_info tpi; int i; bool csum_err = false; if (parse_gre_header(skb, &tpi, &csum_err) < 0) goto drop; rcu_read_lock(); for (i = 0; i < GRE_IP_PROTO_MAX; i++) { struct gre_cisco_protocol *proto; int ret; proto = rcu_dereference(gre_cisco_proto_list[i]); if (!proto) continue; ret = proto->handler(skb, &tpi); if (ret == PACKET_RCVD) { rcu_read_unlock(); return 0; } } rcu_read_unlock(); icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0); drop: kfree_skb(skb); return 0; } static void gre_cisco_err(struct sk_buff *skb, u32 info) { /* All the routers (except for Linux) return only * 8 bytes of packet payload. It means, that precise relaying of * ICMP in the real Internet is absolutely infeasible. * * Moreover, Cisco "wise men" put GRE key to the third word * in GRE header. It makes impossible maintaining even soft * state for keyed * GRE tunnels with enabled checksum. Tell them "thank you". * * Well, I wonder, rfc1812 was written by Cisco employee, * what the hell these idiots break standards established * by themselves??? */ const int type = icmp_hdr(skb)->type; const int code = icmp_hdr(skb)->code; struct tnl_ptk_info tpi; bool csum_err = false; int i; if (parse_gre_header(skb, &tpi, &csum_err)) { if (!csum_err) /* ignore csum errors. */ return; } if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) { ipv4_update_pmtu(skb, dev_net(skb->dev), info, skb->dev->ifindex, 0, IPPROTO_GRE, 0); return; } if (type == ICMP_REDIRECT) { ipv4_redirect(skb, dev_net(skb->dev), skb->dev->ifindex, 0, IPPROTO_GRE, 0); return; } rcu_read_lock(); for (i = 0; i < GRE_IP_PROTO_MAX; i++) { struct gre_cisco_protocol *proto; proto = rcu_dereference(gre_cisco_proto_list[i]); if (!proto) continue; if (proto->err_handler(skb, info, &tpi) == PACKET_RCVD) goto out; } out: rcu_read_unlock(); } static int gre_rcv(struct sk_buff *skb) { const struct gre_protocol *proto; u8 ver; int ret; if (!pskb_may_pull(skb, 12)) goto drop; ver = skb->data[1]&0x7f; if (ver >= GREPROTO_MAX) goto drop; rcu_read_lock(); proto = rcu_dereference(gre_proto[ver]); if (!proto || !proto->handler) goto drop_unlock; ret = proto->handler(skb); rcu_read_unlock(); return ret; drop_unlock: rcu_read_unlock(); drop: kfree_skb(skb); return NET_RX_DROP; } static void gre_err(struct sk_buff *skb, u32 info) { const struct gre_protocol *proto; const struct iphdr *iph = (const struct iphdr *)skb->data; u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f; if (ver >= GREPROTO_MAX) return; rcu_read_lock(); proto = rcu_dereference(gre_proto[ver]); if (proto && proto->err_handler) proto->err_handler(skb, info); rcu_read_unlock(); } static const struct net_protocol net_gre_protocol = { .handler = gre_rcv, .err_handler = gre_err, .netns_ok = 1, }; static const struct gre_protocol ipgre_protocol = { .handler = gre_cisco_rcv, .err_handler = gre_cisco_err, }; int gre_cisco_register(struct gre_cisco_protocol *newp) { struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **) &gre_cisco_proto_list[newp->priority]; return (cmpxchg(proto, NULL, newp) == NULL) ? 0 : -EBUSY; } EXPORT_SYMBOL_GPL(gre_cisco_register); int gre_cisco_unregister(struct gre_cisco_protocol *del_proto) { struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **) &gre_cisco_proto_list[del_proto->priority]; int ret; ret = (cmpxchg(proto, del_proto, NULL) == del_proto) ? 0 : -EINVAL; if (ret) return ret; synchronize_net(); return 0; } EXPORT_SYMBOL_GPL(gre_cisco_unregister); static int __init gre_init(void) { pr_info("GRE over IPv4 demultiplexor driver\n"); if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) { pr_err("can't add protocol\n"); goto err; } if (gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO) < 0) { pr_info("%s: can't add ipgre handler\n", __func__); goto err_gre; } if (gre_offload_init()) { pr_err("can't add protocol offload\n"); goto err_gso; } return 0; err_gso: gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO); err_gre: inet_del_protocol(&net_gre_protocol, IPPROTO_GRE); err: return -EAGAIN; } static void __exit gre_exit(void) { gre_offload_exit(); gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO); inet_del_protocol(&net_gre_protocol, IPPROTO_GRE); } module_init(gre_init); module_exit(gre_exit); MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver"); MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)"); MODULE_LICENSE("GPL");