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