Function icmp6_error

freebsd/netinet6/icmp6.c:258–391

* Generate an error packet of type error in response to bad IP6 packet. */

 * Generate an error packet of type error in response to bad IP6 packet.
 */
void
icmp6_error(struct mbuf *m, int type, int code, int param)
{
	struct ip6_hdr *oip6, *nip6;
	struct icmp6_hdr *icmp6;
	u_int preplen;
	int off;
	int nxt;

	ICMP6STAT_INC(icp6s_error);

	/* count per-type-code statistics */
	icmp6_errcount(type, code);

#ifdef M_DECRYPTED	/*not openbsd*/
	if (m->m_flags & M_DECRYPTED) {
		ICMP6STAT_INC(icp6s_canterror);
		goto freeit;
	}
#endif

	if (m->m_len < sizeof(struct ip6_hdr)) {
		m = m_pullup(m, sizeof(struct ip6_hdr));
		if (m == NULL) {
			IP6STAT_INC(ip6s_exthdrtoolong);
			return;
		}
	}
	oip6 = mtod(m, struct ip6_hdr *);

	/*
	 * If the destination address of the erroneous packet is a multicast
	 * address, or the packet was sent using link-layer multicast,
	 * we should basically suppress sending an error (RFC 2463, Section
	 * 2.4).
	 * We have two exceptions (the item e.2 in that section):
	 * - the Packet Too Big message can be sent for path MTU discovery.
	 * - the Parameter Problem Message that can be allowed an icmp6 error
	 *   in the option type field.  This check has been done in
	 *   ip6_unknown_opt(), so we can just check the type and code.
	 */
	if ((m->m_flags & (M_BCAST|M_MCAST) ||
	     IN6_IS_ADDR_MULTICAST(&oip6->ip6_dst)) &&
	    (type != ICMP6_PACKET_TOO_BIG &&
	     (type != ICMP6_PARAM_PROB ||
	      code != ICMP6_PARAMPROB_OPTION)))
		goto freeit;

	/*
	 * RFC 2463, 2.4 (e.5): source address check.
	 * XXX: the case of anycast source?
	 */
	if (IN6_IS_ADDR_UNSPECIFIED(&oip6->ip6_src) ||
	    IN6_IS_ADDR_MULTICAST(&oip6->ip6_src))
		goto freeit;

	/*
	 * If we are about to send ICMPv6 against ICMPv6 error/redirect,