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 struct dst_entry *dst = NULL; 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 nf_route(nft_net(pkt), &dst, &fl, false, nft_pf(pkt)); 47 if (dst) { 48 mtu = min(mtu, dst_mtu(dst)); 49 dst_release(dst); 50 } 51 52 if (mtu <= minlen || mtu > 0xffff) 53 return TCP_MSS_DEFAULT; 54 55 return mtu - minlen; 56 } 57 58 static void nft_rt_get_eval(const struct nft_expr *expr, 59 struct nft_regs *regs, 60 const struct nft_pktinfo *pkt) 61 { 62 const struct nft_rt *priv = nft_expr_priv(expr); 63 const struct sk_buff *skb = pkt->skb; 64 u32 *dest = ®s->data[priv->dreg]; 65 const struct dst_entry *dst; 66 67 dst = skb_dst(skb); 68 if (!dst) 69 goto err; 70 71 switch (priv->key) { 72 #ifdef CONFIG_IP_ROUTE_CLASSID 73 case NFT_RT_CLASSID: 74 *dest = dst->tclassid; 75 break; 76 #endif 77 case NFT_RT_NEXTHOP4: 78 if (nft_pf(pkt) != NFPROTO_IPV4) 79 goto err; 80 81 *dest = (__force u32)rt_nexthop((const struct rtable *)dst, 82 ip_hdr(skb)->daddr); 83 break; 84 case NFT_RT_NEXTHOP6: 85 if (nft_pf(pkt) != NFPROTO_IPV6) 86 goto err; 87 88 memcpy(dest, rt6_nexthop((struct rt6_info *)dst, 89 &ipv6_hdr(skb)->daddr), 90 sizeof(struct in6_addr)); 91 break; 92 case NFT_RT_TCPMSS: 93 nft_reg_store16(dest, get_tcpmss(pkt, dst)); 94 break; 95 default: 96 WARN_ON(1); 97 goto err; 98 } 99 return; 100 101 err: 102 regs->verdict.code = NFT_BREAK; 103 } 104 105 static const struct nla_policy nft_rt_policy[NFTA_RT_MAX + 1] = { 106 [NFTA_RT_DREG] = { .type = NLA_U32 }, 107 [NFTA_RT_KEY] = { .type = NLA_U32 }, 108 }; 109 110 static int nft_rt_get_init(const struct nft_ctx *ctx, 111 const struct nft_expr *expr, 112 const struct nlattr * const tb[]) 113 { 114 struct nft_rt *priv = nft_expr_priv(expr); 115 unsigned int len; 116 117 if (tb[NFTA_RT_KEY] == NULL || 118 tb[NFTA_RT_DREG] == NULL) 119 return -EINVAL; 120 121 priv->key = ntohl(nla_get_be32(tb[NFTA_RT_KEY])); 122 switch (priv->key) { 123 #ifdef CONFIG_IP_ROUTE_CLASSID 124 case NFT_RT_CLASSID: 125 #endif 126 case NFT_RT_NEXTHOP4: 127 len = sizeof(u32); 128 break; 129 case NFT_RT_NEXTHOP6: 130 len = sizeof(struct in6_addr); 131 break; 132 case NFT_RT_TCPMSS: 133 len = sizeof(u16); 134 break; 135 default: 136 return -EOPNOTSUPP; 137 } 138 139 priv->dreg = nft_parse_register(tb[NFTA_RT_DREG]); 140 return nft_validate_register_store(ctx, priv->dreg, NULL, 141 NFT_DATA_VALUE, len); 142 } 143 144 static int nft_rt_get_dump(struct sk_buff *skb, 145 const struct nft_expr *expr) 146 { 147 const struct nft_rt *priv = nft_expr_priv(expr); 148 149 if (nla_put_be32(skb, NFTA_RT_KEY, htonl(priv->key))) 150 goto nla_put_failure; 151 if (nft_dump_register(skb, NFTA_RT_DREG, priv->dreg)) 152 goto nla_put_failure; 153 return 0; 154 155 nla_put_failure: 156 return -1; 157 } 158 159 static int nft_rt_validate(const struct nft_ctx *ctx, const struct nft_expr *expr, 160 const struct nft_data **data) 161 { 162 const struct nft_rt *priv = nft_expr_priv(expr); 163 unsigned int hooks; 164 165 switch (priv->key) { 166 case NFT_RT_NEXTHOP4: 167 case NFT_RT_NEXTHOP6: 168 case NFT_RT_CLASSID: 169 return 0; 170 case NFT_RT_TCPMSS: 171 hooks = (1 << NF_INET_FORWARD) | 172 (1 << NF_INET_LOCAL_OUT) | 173 (1 << NF_INET_POST_ROUTING); 174 break; 175 default: 176 return -EINVAL; 177 } 178 179 return nft_chain_validate_hooks(ctx->chain, hooks); 180 } 181 182 static struct nft_expr_type nft_rt_type; 183 static const struct nft_expr_ops nft_rt_get_ops = { 184 .type = &nft_rt_type, 185 .size = NFT_EXPR_SIZE(sizeof(struct nft_rt)), 186 .eval = nft_rt_get_eval, 187 .init = nft_rt_get_init, 188 .dump = nft_rt_get_dump, 189 .validate = nft_rt_validate, 190 }; 191 192 static struct nft_expr_type nft_rt_type __read_mostly = { 193 .name = "rt", 194 .ops = &nft_rt_get_ops, 195 .policy = nft_rt_policy, 196 .maxattr = NFTA_RT_MAX, 197 .owner = THIS_MODULE, 198 }; 199 200 static int __init nft_rt_module_init(void) 201 { 202 return nft_register_expr(&nft_rt_type); 203 } 204 205 static void __exit nft_rt_module_exit(void) 206 { 207 nft_unregister_expr(&nft_rt_type); 208 } 209 210 module_init(nft_rt_module_init); 211 module_exit(nft_rt_module_exit); 212 213 MODULE_LICENSE("GPL"); 214 MODULE_AUTHOR("Anders K. Pedersen <akp@cohaesio.com>"); 215 MODULE_ALIAS_NFT_EXPR("rt"); 216