/* * "TEE" target extension for Xtables * Copyright © Sebastian Claßen, 2007 * Jan Engelhardt, 2007-2010 * * based on ipt_ROUTE.c from Cédric de Launois * * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * version 2 or later, as published by the Free Software Foundation. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #if IS_ENABLED(CONFIG_NF_CONNTRACK) # define WITH_CONNTRACK 1 # include #endif struct xt_tee_priv { struct notifier_block notifier; struct xt_tee_tginfo *tginfo; int oif; }; static const union nf_inet_addr tee_zero_address; static DEFINE_PER_CPU(bool, tee_active); static struct net *pick_net(struct sk_buff *skb) { #ifdef CONFIG_NET_NS const struct dst_entry *dst; if (skb->dev != NULL) return dev_net(skb->dev); dst = skb_dst(skb); if (dst != NULL && dst->dev != NULL) return dev_net(dst->dev); #endif return &init_net; } static bool tee_tg_route4(struct sk_buff *skb, const struct xt_tee_tginfo *info) { const struct iphdr *iph = ip_hdr(skb); struct net *net = pick_net(skb); struct rtable *rt; struct flowi4 fl4; memset(&fl4, 0, sizeof(fl4)); if (info->priv) { if (info->priv->oif == -1) return false; fl4.flowi4_oif = info->priv->oif; } fl4.daddr = info->gw.ip; fl4.flowi4_tos = RT_TOS(iph->tos); fl4.flowi4_scope = RT_SCOPE_UNIVERSE; rt = ip_route_output_key(net, &fl4); if (IS_ERR(rt)) return false; skb_dst_drop(skb); skb_dst_set(skb, &rt->dst); skb->dev = rt->dst.dev; skb->protocol = htons(ETH_P_IP); return true; } static unsigned int tee_tg4(struct sk_buff *skb, const struct xt_action_param *par) { const struct xt_tee_tginfo *info = par->targinfo; struct iphdr *iph; if (__this_cpu_read(tee_active)) return XT_CONTINUE; /* * Copy the skb, and route the copy. Will later return %XT_CONTINUE for * the original skb, which should continue on its way as if nothing has * happened. The copy should be independently delivered to the TEE * --gateway. */ skb = pskb_copy(skb, GFP_ATOMIC); if (skb == NULL) return XT_CONTINUE; #ifdef WITH_CONNTRACK /* Avoid counting cloned packets towards the original connection. */ nf_conntrack_put(skb->nfct); skb->nfct = &nf_ct_untracked_get()->ct_general; skb->nfctinfo = IP_CT_NEW; nf_conntrack_get(skb->nfct); #endif /* * If we are in PREROUTING/INPUT, the checksum must be recalculated * since the length could have changed as a result of defragmentation. * * We also decrease the TTL to mitigate potential TEE loops * between two hosts. * * Set %IP_DF so that the original source is notified of a potentially * decreased MTU on the clone route. IPv6 does this too. */ iph = ip_hdr(skb); iph->frag_off |= htons(IP_DF); if (par->hooknum == NF_INET_PRE_ROUTING || par->hooknum == NF_INET_LOCAL_IN) --iph->ttl; ip_send_check(iph); if (tee_tg_route4(skb, info)) { __this_cpu_write(tee_active, true); ip_local_out(skb); __this_cpu_write(tee_active, false); } else { kfree_skb(skb); } return XT_CONTINUE; } #if IS_ENABLED(CONFIG_IPV6) static bool tee_tg_route6(struct sk_buff *skb, const struct xt_tee_tginfo *info) { const struct ipv6hdr *iph = ipv6_hdr(skb); struct net *net = pick_net(skb); struct dst_entry *dst; struct flowi6 fl6; memset(&fl6, 0, sizeof(fl6)); if (info->priv) { if (info->priv->oif == -1) return false; fl6.flowi6_oif = info->priv->oif; } fl6.daddr = info->gw.in6; fl6.flowlabel = ((iph->flow_lbl[0] & 0xF) << 16) | (iph->flow_lbl[1] << 8) | iph->flow_lbl[2]; dst = ip6_route_output(net, NULL, &fl6); if (dst->error) { dst_release(dst); return false; } skb_dst_drop(skb); skb_dst_set(skb, dst); skb->dev = dst->dev; skb->protocol = htons(ETH_P_IPV6); return true; } static unsigned int tee_tg6(struct sk_buff *skb, const struct xt_action_param *par) { const struct xt_tee_tginfo *info = par->targinfo; if (__this_cpu_read(tee_active)) return XT_CONTINUE; skb = pskb_copy(skb, GFP_ATOMIC); if (skb == NULL) return XT_CONTINUE; #ifdef WITH_CONNTRACK nf_conntrack_put(skb->nfct); skb->nfct = &nf_ct_untracked_get()->ct_general; skb->nfctinfo = IP_CT_NEW; nf_conntrack_get(skb->nfct); #endif if (par->hooknum == NF_INET_PRE_ROUTING || par->hooknum == NF_INET_LOCAL_IN) { struct ipv6hdr *iph = ipv6_hdr(skb); --iph->hop_limit; } if (tee_tg_route6(skb, info)) { __this_cpu_write(tee_active, true); ip6_local_out(skb); __this_cpu_write(tee_active, false); } else { kfree_skb(skb); } return XT_CONTINUE; } #endif static int tee_netdev_event(struct notifier_block *this, unsigned long event, void *ptr) { struct net_device *dev = ptr; struct xt_tee_priv *priv; priv = container_of(this, struct xt_tee_priv, notifier); switch (event) { case NETDEV_REGISTER: if (!strcmp(dev->name, priv->tginfo->oif)) priv->oif = dev->ifindex; break; case NETDEV_UNREGISTER: if (dev->ifindex == priv->oif) priv->oif = -1; break; case NETDEV_CHANGENAME: if (!strcmp(dev->name, priv->tginfo->oif)) priv->oif = dev->ifindex; else if (dev->ifindex == priv->oif) priv->oif = -1; break; } return NOTIFY_DONE; } static int tee_tg_check(const struct xt_tgchk_param *par) { struct xt_tee_tginfo *info = par->targinfo; struct xt_tee_priv *priv; /* 0.0.0.0 and :: not allowed */ if (memcmp(&info->gw, &tee_zero_address, sizeof(tee_zero_address)) == 0) return -EINVAL; if (info->oif[0]) { if (info->oif[sizeof(info->oif)-1] != '\0') return -EINVAL; priv = kzalloc(sizeof(*priv), GFP_KERNEL); if (priv == NULL) return -ENOMEM; priv->tginfo = info; priv->oif = -1; priv->notifier.notifier_call = tee_netdev_event; info->priv = priv; register_netdevice_notifier(&priv->notifier); } else info->priv = NULL; return 0; } static void tee_tg_destroy(const struct xt_tgdtor_param *par) { struct xt_tee_tginfo *info = par->targinfo; if (info->priv) { unregister_netdevice_notifier(&info->priv->notifier); kfree(info->priv); } } static struct xt_target tee_tg_reg[] __read_mostly = { { .name = "TEE", .revision = 1, .family = NFPROTO_IPV4, .target = tee_tg4, .targetsize = sizeof(struct xt_tee_tginfo), .checkentry = tee_tg_check, .destroy = tee_tg_destroy, .me = THIS_MODULE, }, #if IS_ENABLED(CONFIG_IPV6) { .name = "TEE", .revision = 1, .family = NFPROTO_IPV6, .target = tee_tg6, .targetsize = sizeof(struct xt_tee_tginfo), .checkentry = tee_tg_check, .destroy = tee_tg_destroy, .me = THIS_MODULE, }, #endif }; static int __init tee_tg_init(void) { return xt_register_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg)); } static void __exit tee_tg_exit(void) { xt_unregister_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg)); } module_init(tee_tg_init); module_exit(tee_tg_exit); MODULE_AUTHOR("Sebastian Claßen "); MODULE_AUTHOR("Jan Engelhardt "); MODULE_DESCRIPTION("Xtables: Reroute packet copy"); MODULE_LICENSE("GPL"); MODULE_ALIAS("ipt_TEE"); MODULE_ALIAS("ip6t_TEE");