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// SPDX-License-Identifier: GPL-2.0-only
#include <linux/skbuff.h>
#include <net/addrconf.h>
#include <net/ip6_checksum.h>
#include <net/ipv6.h>
#include <net/ndisc.h>
static int ndisc_check_ip6hdr(struct sk_buff *skb)
{
const struct ipv6hdr *ip6h;
unsigned int offset, len;
offset = skb_network_offset(skb) + sizeof(*ip6h);
if (!pskb_may_pull(skb, offset))
return -EINVAL;
ip6h = ipv6_hdr(skb);
if (ip6h->version != 6)
return -EINVAL;
if (ip6h->nexthdr != IPPROTO_ICMPV6)
return -ENOMSG;
/* RFC 4861 7.1.1 / 7.1.2: must not have been forwarded by a router */
if (ip6h->hop_limit != 255)
return -EINVAL;
len = offset + ntohs(ip6h->payload_len);
if (skb->len < len || len <= offset)
return -EINVAL;
skb_set_transport_header(skb, offset);
return 0;
}
static __sum16 ndisc_validate_checksum(struct sk_buff *skb)
{
return skb_checksum_validate(skb, IPPROTO_ICMPV6, ip6_compute_pseudo);
}
static int ndisc_check_icmpv6(struct sk_buff *skb)
{
unsigned int len = skb_transport_offset(skb) + sizeof(struct icmp6hdr);
unsigned int transport_len = ipv6_transport_len(skb);
struct sk_buff *skb_chk;
struct icmp6hdr *hdr;
if (!pskb_may_pull(skb, len))
return -EINVAL;
/* RFC 4861 7.1.1 / 7.1.2: the ICMPv6 checksum must be valid */
skb_chk = skb_checksum_trimmed(skb, transport_len,
ndisc_validate_checksum);
if (!skb_chk)
return -EINVAL;
if (skb_chk != skb)
kfree_skb(skb_chk);
/* RFC 4861 7.1.1 / 7.1.2: Code must be 0 */
hdr = (struct icmp6hdr *)skb_transport_header(skb);
if (hdr->icmp6_code != 0)
return -EINVAL;
return 0;
}
static int ndisc_check_options(struct sk_buff *skb, unsigned int opts_len,
bool reject_slla)
{
unsigned int offset = skb_transport_offset(skb) + sizeof(struct nd_msg);
struct nd_opt_hdr *opt, _opt;
while (opts_len > 0) {
if (opts_len < sizeof(*opt))
return -EINVAL;
opt = skb_header_pointer(skb, offset, sizeof(_opt), &_opt);
if (!opt)
return -EINVAL;
/* RFC 4861 7.1.1 / 7.1.2: all option lengths must be > 0 */
if (!opt->nd_opt_len)
return -EINVAL;
/* RFC 4861 7.1.1: DAD NS must not contain a source link-layer
* address option
*/
if (reject_slla && opt->nd_opt_type == ND_OPT_SOURCE_LL_ADDR)
return -EINVAL;
if (opt->nd_opt_len * 8 > opts_len)
return -EINVAL;
offset += opt->nd_opt_len * 8;
opts_len -= opt->nd_opt_len * 8;
}
return 0;
}
static int ndisc_check_nd_msg(struct sk_buff *skb)
{
unsigned int len = skb_transport_offset(skb) + sizeof(struct nd_msg);
unsigned int transport_len = ipv6_transport_len(skb);
bool reject_slla = false;
const struct nd_msg *msg;
if (!pskb_may_pull(skb, len))
return -EINVAL;
/* RFC 4861 7.1.1 / 7.1.2: ICMP length is at least sizeof(nd_msg) */
if (transport_len < sizeof(struct nd_msg))
return -EINVAL;
msg = (struct nd_msg *)skb_transport_header(skb);
/* RFC 4861 7.1.1 / 7.1.2: Target Address must not be a
* multicast address
*/
if (ipv6_addr_is_multicast(&msg->target))
return -EINVAL;
switch (msg->icmph.icmp6_type) {
case NDISC_NEIGHBOUR_SOLICITATION:
if (ipv6_addr_any(&ipv6_hdr(skb)->saddr)) {
/* RFC 4861 7.1.1: DAD NS destination must be a
* solicited-node multicast address
*/
if (!ipv6_addr_is_solict_mult(&ipv6_hdr(skb)->daddr))
return -EINVAL;
/* RFC 4861 7.1.1: DAD NS must not contain a source
* link-layer address option
*/
reject_slla = true;
}
break;
case NDISC_NEIGHBOUR_ADVERTISEMENT:
/* RFC 4861 7.1.2: Solicited flag must be 0 for
* multicast destinations
*/
if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr) &&
msg->icmph.icmp6_solicited)
return -EINVAL;
break;
default:
return -ENODATA;
}
return ndisc_check_options(skb, transport_len - sizeof(struct nd_msg),
reject_slla);
}
/**
* ndisc_check_ns_na - validate an NS/NA packet and set its transport header
* @skb: the skb to validate
*
* Validates an IPv6 packet for compliance with RFC 4861 sections 7.1.1
* (Neighbor Solicitation) and 7.1.2 (Neighbor Advertisement). If valid,
* sets the skb transport header.
*
* Caller needs to set the skb network header.
*
* Return:
* * 0 - valid NS/NA; the skb transport header has been set.
* * -EINVAL - a broken packet was detected, i.e. it violates some
* internet standard.
* * -ENOMSG - IP header validation succeeded but it is not an ICMPv6
* packet.
* * -ENODATA - IP+ICMPv6 header validation succeeded but it is not a
* Neighbor Solicitation or Neighbor Advertisement.
*/
int ndisc_check_ns_na(struct sk_buff *skb)
{
int ret;
ret = ndisc_check_ip6hdr(skb);
if (ret < 0)
return ret;
ret = ndisc_check_icmpv6(skb);
if (ret < 0)
return ret;
return ndisc_check_nd_msg(skb);
}
EXPORT_SYMBOL_GPL(ndisc_check_ns_na);
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