1 /* 2 * Copyright (c) 2016 Anders K. Pedersen <akp@cohaesio.com> 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License version 2 as 6 * published by the Free Software Foundation. 7 */ 8 9 #include <linux/kernel.h> 10 #include <linux/init.h> 11 #include <linux/module.h> 12 #include <linux/netlink.h> 13 #include <linux/netfilter.h> 14 #include <linux/netfilter/nf_tables.h> 15 #include <net/dst.h> 16 #include <net/ip6_route.h> 17 #include <net/route.h> 18 #include <net/netfilter/nf_tables.h> 19 #include <net/netfilter/nf_tables_core.h> 20 21 struct nft_rt { 22 enum nft_rt_keys key:8; 23 enum nft_registers dreg:8; 24 }; 25 26 static u16 get_tcpmss(const struct nft_pktinfo *pkt, const struct dst_entry *skbdst) 27 { 28 u32 minlen = sizeof(struct ipv6hdr), mtu = dst_mtu(skbdst); 29 const struct sk_buff *skb = pkt->skb; 30 const struct nf_afinfo *ai; 31 struct flowi fl; 32 33 memset(&fl, 0, sizeof(fl)); 34 35 switch (nft_pf(pkt)) { 36 case NFPROTO_IPV4: 37 fl.u.ip4.daddr = ip_hdr(skb)->saddr; 38 minlen = sizeof(struct iphdr) + sizeof(struct tcphdr); 39 break; 40 case NFPROTO_IPV6: 41 fl.u.ip6.daddr = ipv6_hdr(skb)->saddr; 42 minlen = sizeof(struct ipv6hdr) + sizeof(struct tcphdr); 43 break; 44 } 45 46 ai = nf_get_afinfo(nft_pf(pkt)); 47 if (ai) { 48 struct dst_entry *dst = NULL; 49 50 ai->route(nft_net(pkt), &dst, &fl, false); 51 if (dst) { 52 mtu = min(mtu, dst_mtu(dst)); 53 dst_release(dst); 54 } 55 } 56 57 if (mtu <= minlen || mtu > 0xffff) 58 return TCP_MSS_DEFAULT; 59 60 return mtu - minlen; 61 } 62 63 static void nft_rt_get_eval(const struct nft_expr *expr, 64 struct nft_regs *regs, 65 const struct nft_pktinfo *pkt) 66 { 67 const struct nft_rt *priv = nft_expr_priv(expr); 68 const struct sk_buff *skb = pkt->skb; 69 u32 *dest = ®s->data[priv->dreg]; 70 const struct dst_entry *dst; 71 72 dst = skb_dst(skb); 73 if (!dst) 74 goto err; 75 76 switch (priv->key) { 77 #ifdef CONFIG_IP_ROUTE_CLASSID 78 case NFT_RT_CLASSID: 79 *dest = dst->tclassid; 80 break; 81 #endif 82 case NFT_RT_NEXTHOP4: 83 if (nft_pf(pkt) != NFPROTO_IPV4) 84 goto err; 85 86 *dest = (__force u32)rt_nexthop((const struct rtable *)dst, 87 ip_hdr(skb)->daddr); 88 break; 89 case NFT_RT_NEXTHOP6: 90 if (nft_pf(pkt) != NFPROTO_IPV6) 91 goto err; 92 93 memcpy(dest, rt6_nexthop((struct rt6_info *)dst, 94 &ipv6_hdr(skb)->daddr), 95 sizeof(struct in6_addr)); 96 break; 97 case NFT_RT_TCPMSS: 98 nft_reg_store16(dest, get_tcpmss(pkt, dst)); 99 break; 100 default: 101 WARN_ON(1); 102 goto err; 103 } 104 return; 105 106 err: 107 regs->verdict.code = NFT_BREAK; 108 } 109 110 static const struct nla_policy nft_rt_policy[NFTA_RT_MAX + 1] = { 111 [NFTA_RT_DREG] = { .type = NLA_U32 }, 112 [NFTA_RT_KEY] = { .type = NLA_U32 }, 113 }; 114 115 static int nft_rt_get_init(const struct nft_ctx *ctx, 116 const struct nft_expr *expr, 117 const struct nlattr * const tb[]) 118 { 119 struct nft_rt *priv = nft_expr_priv(expr); 120 unsigned int len; 121 122 if (tb[NFTA_RT_KEY] == NULL || 123 tb[NFTA_RT_DREG] == NULL) 124 return -EINVAL; 125 126 priv->key = ntohl(nla_get_be32(tb[NFTA_RT_KEY])); 127 switch (priv->key) { 128 #ifdef CONFIG_IP_ROUTE_CLASSID 129 case NFT_RT_CLASSID: 130 #endif 131 case NFT_RT_NEXTHOP4: 132 len = sizeof(u32); 133 break; 134 case NFT_RT_NEXTHOP6: 135 len = sizeof(struct in6_addr); 136 break; 137 case NFT_RT_TCPMSS: 138 len = sizeof(u16); 139 break; 140 default: 141 return -EOPNOTSUPP; 142 } 143 144 priv->dreg = nft_parse_register(tb[NFTA_RT_DREG]); 145 return nft_validate_register_store(ctx, priv->dreg, NULL, 146 NFT_DATA_VALUE, len); 147 } 148 149 static int nft_rt_get_dump(struct sk_buff *skb, 150 const struct nft_expr *expr) 151 { 152 const struct nft_rt *priv = nft_expr_priv(expr); 153 154 if (nla_put_be32(skb, NFTA_RT_KEY, htonl(priv->key))) 155 goto nla_put_failure; 156 if (nft_dump_register(skb, NFTA_RT_DREG, priv->dreg)) 157 goto nla_put_failure; 158 return 0; 159 160 nla_put_failure: 161 return -1; 162 } 163 164 static int nft_rt_validate(const struct nft_ctx *ctx, const struct nft_expr *expr, 165 const struct nft_data **data) 166 { 167 const struct nft_rt *priv = nft_expr_priv(expr); 168 unsigned int hooks; 169 170 switch (priv->key) { 171 case NFT_RT_NEXTHOP4: 172 case NFT_RT_NEXTHOP6: 173 case NFT_RT_CLASSID: 174 return 0; 175 case NFT_RT_TCPMSS: 176 hooks = (1 << NF_INET_FORWARD) | 177 (1 << NF_INET_LOCAL_OUT) | 178 (1 << NF_INET_POST_ROUTING); 179 break; 180 default: 181 return -EINVAL; 182 } 183 184 return nft_chain_validate_hooks(ctx->chain, hooks); 185 } 186 187 static struct nft_expr_type nft_rt_type; 188 static const struct nft_expr_ops nft_rt_get_ops = { 189 .type = &nft_rt_type, 190 .size = NFT_EXPR_SIZE(sizeof(struct nft_rt)), 191 .eval = nft_rt_get_eval, 192 .init = nft_rt_get_init, 193 .dump = nft_rt_get_dump, 194 .validate = nft_rt_validate, 195 }; 196 197 static struct nft_expr_type nft_rt_type __read_mostly = { 198 .name = "rt", 199 .ops = &nft_rt_get_ops, 200 .policy = nft_rt_policy, 201 .maxattr = NFTA_RT_MAX, 202 .owner = THIS_MODULE, 203 }; 204 205 static int __init nft_rt_module_init(void) 206 { 207 return nft_register_expr(&nft_rt_type); 208 } 209 210 static void __exit nft_rt_module_exit(void) 211 { 212 nft_unregister_expr(&nft_rt_type); 213 } 214 215 module_init(nft_rt_module_init); 216 module_exit(nft_rt_module_exit); 217 218 MODULE_LICENSE("GPL"); 219 MODULE_AUTHOR("Anders K. Pedersen <akp@cohaesio.com>"); 220 MODULE_ALIAS_NFT_EXPR("rt"); 221