Function ip_output

freebsd/netinet/ip_output.c:318–863

* IP output. The packet in mbuf chain m contains a skeletal IP * header (with len, off, ttl, proto, tos, src, dst). * The mbuf chain containing the packet will be freed. * The mbuf opt, if present, will not be freed. * If route ro is present and has ro_rt initialized, route lookup would be * skipped and ro->ro_rt would be used. If ro is present but ro->ro_rt is NULL, * then result of route

 * inserted, so must have a NULL opt pointer.
 */
int
ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro, int flags,
    struct ip_moptions *imo, struct inpcb *inp)
{
	struct rm_priotracker in_ifa_tracker;
	struct ip *ip;
	struct ifnet *ifp = NULL;	/* keep compiler happy */
	struct mbuf *m0;
	int hlen = sizeof (struct ip);
	int mtu = 0;
	int error = 0;
	int vlan_pcp = -1;
	struct sockaddr_in *dst, sin;
	const struct sockaddr_in *gw;
	struct in_ifaddr *ia = NULL;
	struct in_addr src;
	int isbroadcast;
	uint16_t ip_len, ip_off;
	uint32_t fibnum;
#if defined(IPSEC) || defined(IPSEC_SUPPORT)
	int no_route_but_check_spd = 0;
#endif

	M_ASSERTPKTHDR(m);
	NET_EPOCH_ASSERT();

	if (inp != NULL) {
		INP_LOCK_ASSERT(inp);
		M_SETFIB(m, inp->inp_inc.inc_fibnum);
		if ((flags & IP_NODEFAULTFLOWID) == 0) {
			m->m_pkthdr.flowid = inp->inp_flowid;
			M_HASHTYPE_SET(m, inp->inp_flowtype);
		}
		if ((inp->inp_flags2 & INP_2PCP_SET) != 0)
			vlan_pcp = (inp->inp_flags2 & INP_2PCP_MASK) >>
			    INP_2PCP_SHIFT;
#ifdef NUMA
		m->m_pkthdr.numa_domain = inp->inp_numa_domain;
#endif
	}

	if (opt) {
		int len = 0;
		m = ip_insertoptions(m, opt, &len);
		if (len != 0)
			hlen = len; /* ip->ip_hl is updated above */
	}
	ip = mtod(m, struct ip *);
	ip_len = ntohs(ip->ip_len);
	ip_off = ntohs(ip->ip_off);

	if ((flags & (IP_FORWARDING|IP_RAWOUTPUT)) == 0) {
		ip->ip_v = IPVERSION;
		ip->ip_hl = hlen >> 2;
		ip_fillid(ip);
	} else {
		/* Header already set, fetch hlen from there */
		hlen = ip->ip_hl << 2;