1 // SPDX-License-Identifier: GPL-2.0-only
2
3 #include <linux/kernel.h>
4 #include <linux/init.h>
5 #include <linux/module.h>
6 #include <linux/netlink.h>
7 #include <linux/netfilter.h>
8 #include <linux/netfilter/nf_tables.h>
9 #include <net/netfilter/nf_tables_core.h>
10 #include <net/netfilter/nf_tables.h>
11 #include <net/netfilter/nft_fib.h>
12
13 #include <net/ip_fib.h>
14 #include <net/route.h>
15
16 /* don't try to find route from mcast/bcast/zeronet */
17 static __be32 get_saddr(__be32 addr)
18 {
19 if (ipv4_is_multicast(addr) || ipv4_is_lbcast(addr) ||
20 ipv4_is_zeronet(addr))
21 return 0;
22 return addr;
23 }
24
25 #define DSCP_BITS 0xfc
26
27 void nft_fib4_eval_type(const struct nft_expr *expr, struct nft_regs *regs,
28 const struct nft_pktinfo *pkt)
29 {
30 const struct nft_fib *priv = nft_expr_priv(expr);
31 int noff = skb_network_offset(pkt->skb);
32 u32 *dst = ®s->data[priv->dreg];
33 const struct net_device *dev = NULL;
34 struct iphdr *iph, _iph;
35 __be32 addr;
36
37 if (priv->flags & NFTA_FIB_F_IIF)
38 dev = nft_in(pkt);
39 else if (priv->flags & NFTA_FIB_F_OIF)
40 dev = nft_out(pkt);
41
42 iph = skb_header_pointer(pkt->skb, noff, sizeof(_iph), &_iph);
43 if (!iph) {
44 regs->verdict.code = NFT_BREAK;
45 return;
46 }
47
48 if (priv->flags & NFTA_FIB_F_DADDR)
49 addr = iph->daddr;
50 else
51 addr = iph->saddr;
52
53 *dst = inet_dev_addr_type(nft_net(pkt), dev, addr);
54 }
55 EXPORT_SYMBOL_GPL(nft_fib4_eval_type);
56
57 void nft_fib4_eval(const struct nft_expr *expr, struct nft_regs *regs,
58 const struct nft_pktinfo *pkt)
59 {
60 const struct nft_fib *priv = nft_expr_priv(expr);
61 int noff = skb_network_offset(pkt->skb);
62 u32 *dest = ®s->data[priv->dreg];
63 struct iphdr *iph, _iph;
64 struct fib_result res;
65 struct flowi4 fl4 = {
66 .flowi4_scope = RT_SCOPE_UNIVERSE,
67 .flowi4_iif = LOOPBACK_IFINDEX,
68 .flowi4_uid = sock_net_uid(nft_net(pkt), NULL),
69 };
70 const struct net_device *oif;
71 const struct net_device *found;
72
73 /*
74 * Do not set flowi4_oif, it restricts results (for example, asking
75 * for oif 3 will get RTN_UNICAST result even if the daddr exits
76 * on another interface.
77 *
78 * Search results for the desired outinterface instead.
79 */
80 if (priv->flags & NFTA_FIB_F_OIF)
81 oif = nft_out(pkt);
82 else if (priv->flags & NFTA_FIB_F_IIF)
83 oif = nft_in(pkt);
84 else
85 oif = NULL;
86
87 if (priv->flags & NFTA_FIB_F_IIF)
88 fl4.flowi4_l3mdev = l3mdev_master_ifindex_rcu(oif);
89
90 if (nft_hook(pkt) == NF_INET_PRE_ROUTING &&
91 nft_fib_is_loopback(pkt->skb, nft_in(pkt))) {
92 nft_fib_store_result(dest, priv, nft_in(pkt));
93 return;
94 }
95
96 iph = skb_header_pointer(pkt->skb, noff, sizeof(_iph), &_iph);
97 if (!iph) {
98 regs->verdict.code = NFT_BREAK;
99 return;
100 }
101
102 if (ipv4_is_zeronet(iph->saddr)) {
103 if (ipv4_is_lbcast(iph->daddr) ||
104 ipv4_is_local_multicast(iph->daddr)) {
105 nft_fib_store_result(dest, priv, pkt->skb->dev);
106 return;
107 }
108 }
109
110 if (priv->flags & NFTA_FIB_F_MARK)
111 fl4.flowi4_mark = pkt->skb->mark;
112
113 fl4.flowi4_tos = iph->tos & DSCP_BITS;
114
115 if (priv->flags & NFTA_FIB_F_DADDR) {
116 fl4.daddr = iph->daddr;
117 fl4.saddr = get_saddr(iph->saddr);
118 } else {
119 if (nft_hook(pkt) == NF_INET_FORWARD &&
120 priv->flags & NFTA_FIB_F_IIF)
121 fl4.flowi4_iif = nft_out(pkt)->ifindex;
122
123 fl4.daddr = iph->saddr;
124 fl4.saddr = get_saddr(iph->daddr);
125 }
126
127 *dest = 0;
128
129 if (fib_lookup(nft_net(pkt), &fl4, &res, FIB_LOOKUP_IGNORE_LINKSTATE))
130 return;
131
132 switch (res.type) {
133 case RTN_UNICAST:
134 break;
135 case RTN_LOCAL: /* Should not see RTN_LOCAL here */
136 return;
137 default:
138 break;
139 }
140
141 if (!oif) {
142 found = FIB_RES_DEV(res);
143 } else {
144 if (!fib_info_nh_uses_dev(res.fi, oif))
145 return;
146 found = oif;
147 }
148
149 nft_fib_store_result(dest, priv, found);
150 }
151 EXPORT_SYMBOL_GPL(nft_fib4_eval);
152
153 static struct nft_expr_type nft_fib4_type;
154
155 static const struct nft_expr_ops nft_fib4_type_ops = {
156 .type = &nft_fib4_type,
157 .size = NFT_EXPR_SIZE(sizeof(struct nft_fib)),
158 .eval = nft_fib4_eval_type,
159 .init = nft_fib_init,
160 .dump = nft_fib_dump,
161 .validate = nft_fib_validate,
162 .reduce = nft_fib_reduce,
163 };
164
165 static const struct nft_expr_ops nft_fib4_ops = {
166 .type = &nft_fib4_type,
167 .size = NFT_EXPR_SIZE(sizeof(struct nft_fib)),
168 .eval = nft_fib4_eval,
169 .init = nft_fib_init,
170 .dump = nft_fib_dump,
171 .validate = nft_fib_validate,
172 .reduce = nft_fib_reduce,
173 };
174
175 static const struct nft_expr_ops *
176 nft_fib4_select_ops(const struct nft_ctx *ctx,
177 const struct nlattr * const tb[])
178 {
179 enum nft_fib_result result;
180
181 if (!tb[NFTA_FIB_RESULT])
182 return ERR_PTR(-EINVAL);
183
184 result = ntohl(nla_get_be32(tb[NFTA_FIB_RESULT]));
185
186 switch (result) {
187 case NFT_FIB_RESULT_OIF:
188 return &nft_fib4_ops;
189 case NFT_FIB_RESULT_OIFNAME:
190 return &nft_fib4_ops;
191 case NFT_FIB_RESULT_ADDRTYPE:
192 return &nft_fib4_type_ops;
193 default:
194 return ERR_PTR(-EOPNOTSUPP);
195 }
196 }
197
198 static struct nft_expr_type nft_fib4_type __read_mostly = {
199 .name = "fib",
200 .select_ops = nft_fib4_select_ops,
201 .policy = nft_fib_policy,
202 .maxattr = NFTA_FIB_MAX,
203 .family = NFPROTO_IPV4,
204 .owner = THIS_MODULE,
205 };
206
207 static int __init nft_fib4_module_init(void)
208 {
209 return nft_register_expr(&nft_fib4_type);
210 }
211
212 static void __exit nft_fib4_module_exit(void)
213 {
214 nft_unregister_expr(&nft_fib4_type);
215 }
216
217 module_init(nft_fib4_module_init);
218 module_exit(nft_fib4_module_exit);
219 MODULE_LICENSE("GPL");
220 MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
221 MODULE_ALIAS_NFT_AF_EXPR(2, "fib");
222 MODULE_DESCRIPTION("nftables fib / ip route lookup support");
223
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