+ /*
+ * If the state is LISTEN then ignore segment if it contains an RST.
+ * If the segment contains an ACK then it is bad and send a RST.
+ * If it does not contain a SYN then it is not interesting; drop it.
+ * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
+ * tp->iss, and send a segment:
+ * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
+ * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
+ * Fill in remote peer address fields if not previously specified.
+ * Enter SYN_RECEIVED state, and process any other fields of this
+ * segment in this state.
+ */
+ case TCPS_LISTEN: {
+ struct mbuf *am = m_get(M_DONTWAIT);
+ register struct sockaddr_in *sin;
+
+ if (am == 0)
+ goto drop;
+ am->m_len = sizeof (struct sockaddr_in);
+ if (tiflags & TH_RST)
+ goto drop;
+ if (tiflags & TH_ACK)
+ goto dropwithreset;
+ if ((tiflags & TH_SYN) == 0)
+ goto drop;
+ sin = mtod(am, struct sockaddr_in *);
+ sin->sin_family = AF_INET;
+ sin->sin_addr = ti->ti_src;
+ sin->sin_port = ti->ti_sport;
+ laddr = inp->inp_laddr;
+ if (inp->inp_laddr.s_addr == 0)
+ inp->inp_laddr = ti->ti_dst;
+ if (in_pcbconnect(inp, am)) {
+ inp->inp_laddr = laddr;
+ (void) m_free(am);
+ goto drop;