1// SPDX-License-Identifier: GPL-2.0-only
2/* Support nat functions for openvswitch and used by OVS and TC conntrack. */
3
4#include <net/netfilter/nf_nat.h>
5
6/* Modelled after nf_nat_ipv[46]_fn().
7 * range is only used for new, uninitialized NAT state.
8 * Returns either NF_ACCEPT or NF_DROP.
9 */
10static int nf_ct_nat_execute(struct sk_buff *skb, struct nf_conn *ct,
11			     enum ip_conntrack_info ctinfo, int *action,
12			     const struct nf_nat_range2 *range,
13			     enum nf_nat_manip_type maniptype)
14{
15	__be16 proto = skb_protocol(skb, true);
16	int hooknum, err = NF_ACCEPT;
17
18	/* See HOOK2MANIP(). */
19	if (maniptype == NF_NAT_MANIP_SRC)
20		hooknum = NF_INET_LOCAL_IN; /* Source NAT */
21	else
22		hooknum = NF_INET_LOCAL_OUT; /* Destination NAT */
23
24	switch (ctinfo) {
25	case IP_CT_RELATED:
26	case IP_CT_RELATED_REPLY:
27		if (proto == htons(ETH_P_IP) &&
28		    ip_hdr(skb)->protocol == IPPROTO_ICMP) {
29			if (!nf_nat_icmp_reply_translation(skb, ct, ctinfo,
30							   hooknum))
31				err = NF_DROP;
32			goto out;
33		} else if (IS_ENABLED(CONFIG_IPV6) && proto == htons(ETH_P_IPV6)) {
34			__be16 frag_off;
35			u8 nexthdr = ipv6_hdr(skb)->nexthdr;
36			int hdrlen = ipv6_skip_exthdr(skb,
37						      sizeof(struct ipv6hdr),
38						      &nexthdr, &frag_off);
39
40			if (hdrlen >= 0 && nexthdr == IPPROTO_ICMPV6) {
41				if (!nf_nat_icmpv6_reply_translation(skb, ct,
42								     ctinfo,
43								     hooknum,
44								     hdrlen))
45					err = NF_DROP;
46				goto out;
47			}
48		}
49		/* Non-ICMP, fall thru to initialize if needed. */
50		fallthrough;
51	case IP_CT_NEW:
52		/* Seen it before?  This can happen for loopback, retrans,
53		 * or local packets.
54		 */
55		if (!nf_nat_initialized(ct, maniptype)) {
56			/* Initialize according to the NAT action. */
57			err = (range && range->flags & NF_NAT_RANGE_MAP_IPS)
58				/* Action is set up to establish a new
59				 * mapping.
60				 */
61				? nf_nat_setup_info(ct, range, maniptype)
62				: nf_nat_alloc_null_binding(ct, hooknum);
63			if (err != NF_ACCEPT)
64				goto out;
65		}
66		break;
67
68	case IP_CT_ESTABLISHED:
69	case IP_CT_ESTABLISHED_REPLY:
70		break;
71
72	default:
73		err = NF_DROP;
74		goto out;
75	}
76
77	err = nf_nat_packet(ct, ctinfo, hooknum, skb);
78out:
79	if (err == NF_ACCEPT)
80		*action |= BIT(maniptype);
81
82	return err;
83}
84
85int nf_ct_nat(struct sk_buff *skb, struct nf_conn *ct,
86	      enum ip_conntrack_info ctinfo, int *action,
87	      const struct nf_nat_range2 *range, bool commit)
88{
89	enum nf_nat_manip_type maniptype;
90	int err, ct_action = *action;
91
92	*action = 0;
93
94	/* Add NAT extension if not confirmed yet. */
95	if (!nf_ct_is_confirmed(ct) && !nf_ct_nat_ext_add(ct))
96		return NF_DROP;   /* Can't NAT. */
97
98	if (ctinfo != IP_CT_NEW && (ct->status & IPS_NAT_MASK) &&
99	    (ctinfo != IP_CT_RELATED || commit)) {
100		/* NAT an established or related connection like before. */
101		if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY)
102			/* This is the REPLY direction for a connection
103			 * for which NAT was applied in the forward
104			 * direction.  Do the reverse NAT.
105			 */
106			maniptype = ct->status & IPS_SRC_NAT
107				? NF_NAT_MANIP_DST : NF_NAT_MANIP_SRC;
108		else
109			maniptype = ct->status & IPS_SRC_NAT
110				? NF_NAT_MANIP_SRC : NF_NAT_MANIP_DST;
111	} else if (ct_action & BIT(NF_NAT_MANIP_SRC)) {
112		maniptype = NF_NAT_MANIP_SRC;
113	} else if (ct_action & BIT(NF_NAT_MANIP_DST)) {
114		maniptype = NF_NAT_MANIP_DST;
115	} else {
116		return NF_ACCEPT;
117	}
118
119	err = nf_ct_nat_execute(skb, ct, ctinfo, action, range, maniptype);
120	if (err == NF_ACCEPT && ct->status & IPS_DST_NAT) {
121		if (ct->status & IPS_SRC_NAT) {
122			if (maniptype == NF_NAT_MANIP_SRC)
123				maniptype = NF_NAT_MANIP_DST;
124			else
125				maniptype = NF_NAT_MANIP_SRC;
126
127			err = nf_ct_nat_execute(skb, ct, ctinfo, action, range,
128						maniptype);
129		} else if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
130			err = nf_ct_nat_execute(skb, ct, ctinfo, action, NULL,
131						NF_NAT_MANIP_SRC);
132		}
133	}
134	return err;
135}
136EXPORT_SYMBOL_GPL(nf_ct_nat);
137