/**
* Connects to another host. The function given as the "connected"
* argument will be called when the connection has been established.
*
* @param pcb the tcp_pcb used to establish the connection
* @param ipaddr the remote ip address to connect to
* @param port the remote tcp port to connect to
* @param connected callback function to call when connected (or on error)
* @return ERR_VAL if invalid arguments are given
* ERR_OK if connect request has been sent
* other err_t values if connect request couldn't be sent
*/
err_t
tcp_connect(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port,
err_t (* connected)(void *arg, struct tcp_pcb *tpcb, err_t err))
{
u32_t optdata;
err_t ret;
u32_t iss;
LWIP_ERROR("tcp_connect: can only connected from state CLOSED", pcb->state == CLOSED, return ERR_ISCONN);
LWIP_DEBUGF(TCP_DEBUG, ("tcp_connect to port %"U16_F"\n", port));
if (ipaddr != NULL) {
pcb->remote_ip = *ipaddr;
} else {
return ERR_VAL;
}
pcb->remote_port = port;
if (pcb->local_port == 0) {
pcb->local_port = tcp_new_port();
}
iss = tcp_next_iss();
pcb->rcv_nxt = 0;
pcb->snd_nxt = iss;
pcb->lastack = iss - 1;
pcb->snd_lbb = iss - 1;
pcb->rcv_wnd = TCP_WND;
pcb->rcv_ann_wnd = TCP_WND;
pcb->snd_wnd = TCP_WND;
/* As initial send MSS, we use TCP_MSS but limit it to 536.
The send MSS is updated when an MSS option is received. */
pcb->mss = (TCP_MSS > 536) ? 536 : TCP_MSS;
#if TCP_CALCULATE_EFF_SEND_MSS
pcb->mss = tcp_eff_send_mss(pcb->mss, ipaddr);
#endif /* TCP_CALCULATE_EFF_SEND_MSS */
pcb->cwnd = 1;
pcb->ssthresh = pcb->mss * 10;
pcb->state = SYN_SENT;
#if LWIP_CALLBACK_API
pcb->connected = connected;
#endif /* LWIP_CALLBACK_API */
TCP_RMV(&tcp_bound_pcbs, pcb);
TCP_REG(&tcp_active_pcbs, pcb);
snmp_inc_tcpactiveopens();
/* Build an MSS option */
optdata = TCP_BUILD_MSS_OPTION();
ret = tcp_enqueue(pcb, NULL, 0, TCP_SYN, 0, (u8_t *)&optdata, 4);
if (ret == ERR_OK) {
tcp_output(pcb);
}
return ret;
}
/**
* Called by tcp_input() when a segment arrives for a listening
* connection (from tcp_input()).
*
* @param pcb the tcp_pcb_listen for which a segment arrived
* @return ERR_OK if the segment was processed
* another err_t on error
*
* @note the return value is not (yet?) used in tcp_input()
* @note the segment which arrived is saved in global variables, therefore only the pcb
* involved is passed as a parameter to this function
*/
static err_t
tcp_listen_input(struct tcp_pcb_listen *pcb)
{
struct tcp_pcb *npcb;
u32_t optdata;
/* In the LISTEN state, we check for incoming SYN segments,
creates a new PCB, and responds with a SYN|ACK. */
if (flags & TCP_ACK) {
/* For incoming segments with the ACK flag set, respond with a
RST. */
LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_listen_input: ACK in LISTEN, sending reset\n"));
tcp_rst(ackno + 1, seqno + tcplen,
&(iphdr->dest), &(iphdr->src),
tcphdr->dest, tcphdr->src);
} else if (flags & TCP_SYN) {
LWIP_DEBUGF(TCP_DEBUG, ("TCP connection request %"U16_F" -> %"U16_F".\n", tcphdr->src, tcphdr->dest));
#if TCP_LISTEN_BACKLOG
if (pcb->accepts_pending >= pcb->backlog) {
return ERR_ABRT;
}
#endif /* TCP_LISTEN_BACKLOG */
npcb = tcp_alloc(pcb->prio);
/* If a new PCB could not be created (probably due to lack of memory),
we don't do anything, but rely on the sender will retransmit the
SYN at a time when we have more memory available. */
if (npcb == NULL) {
LWIP_DEBUGF(TCP_DEBUG, ("tcp_listen_input: could not allocate PCB\n"));
TCP_STATS_INC(tcp.memerr);
return ERR_MEM;
}
#if TCP_LISTEN_BACKLOG
pcb->accepts_pending++;
#endif /* TCP_LISTEN_BACKLOG */
/* Set up the new PCB. */
ip_addr_set(&(npcb->local_ip), &(iphdr->dest));
npcb->local_port = pcb->local_port;
ip_addr_set(&(npcb->remote_ip), &(iphdr->src));
npcb->remote_port = tcphdr->src;
npcb->state = SYN_RCVD;
npcb->rcv_nxt = seqno + 1;
npcb->snd_wnd = tcphdr->wnd;
npcb->ssthresh = npcb->snd_wnd;
npcb->snd_wl1 = seqno - 1;/* initialise to seqno-1 to force window update */
npcb->callback_arg = pcb->callback_arg;
#if LWIP_CALLBACK_API
npcb->accept = pcb->accept;
#endif /* LWIP_CALLBACK_API */
/* inherit socket options */
npcb->so_options = pcb->so_options & (SOF_DEBUG|SOF_DONTROUTE|SOF_KEEPALIVE|SOF_OOBINLINE|SOF_LINGER);
/* Register the new PCB so that we can begin receiving segments
for it. */
TCP_REG(&tcp_active_pcbs, npcb);
/* Parse any options in the SYN. */
tcp_parseopt(npcb);
#if TCP_CALCULATE_EFF_SEND_MSS
npcb->mss = tcp_eff_send_mss(npcb->mss, &(npcb->remote_ip));
#endif /* TCP_CALCULATE_EFF_SEND_MSS */
snmp_inc_tcppassiveopens();
/* Build an MSS option. */
optdata = TCP_BUILD_MSS_OPTION();
/* Send a SYN|ACK together with the MSS option. */
tcp_enqueue(npcb, NULL, 0, TCP_SYN | TCP_ACK, 0, (u8_t *)&optdata, 4);
return tcp_output(npcb);
}
return ERR_OK;
}
/**
* Called by tcp_output() to actually send a TCP segment over IP.
*
* @param seg the tcp_seg to send
* @param pcb the tcp_pcb for the TCP connection used to send the segment
*/
static void
tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb)
{
u16_t len;
u32_t *opts;
/* The TCP header has already been constructed, but the ackno and
wnd fields remain. */
seg->tcphdr->ackno = htonl(pcb->rcv_nxt);
/* advertise our receive window size in this TCP segment */
seg->tcphdr->wnd = RCV_WND_SCALE(pcb, pcb->rcv_ann_wnd); // Which means: htons(pcb->rcv_ann_wnd >> pcb->rcv_scale);
pcb->rcv_ann_right_edge = pcb->rcv_nxt + pcb->rcv_ann_wnd;
/* Add any requested options. NB MSS option is only set on SYN
packets, so ignore it here */
LWIP_ASSERT("seg->tcphdr not aligned", ((mem_ptr_t)(seg->tcphdr + 1) % 4) == 0);
opts = (u32_t *)(void *)(seg->tcphdr + 1);
if (seg->flags & TF_SEG_OPTS_MSS) {
TCP_BUILD_MSS_OPTION(*opts, pcb->advtsd_mss);
opts += 1; // Move to the next line (meaning next 32 bit) as this option is 4 bytes long
}
/* If RCV_SCALE is set then prepare segment for window scaling option */
if (seg->flags & TF_SEG_OPTS_WNDSCALE) {
TCP_BUILD_WNDSCALE_OPTION(*opts, pcb->rcv_scale);
opts += 1; // Move to the next line (meaning next 32 bit) as this option is 3 bytes long + we added 1 byte NOOP padding => total 4 bytes
}
#if LWIP_TCP_TIMESTAMPS
pcb->ts_lastacksent = pcb->rcv_nxt;
if (seg->flags & TF_SEG_OPTS_TS) {
tcp_build_timestamp_option(pcb, opts);
opts += 3; // Move to the next line (meaning next 32 bit) as this option is 10 bytes long, 12 with padding (so jump 3 lines)
}
#endif
/* If we don't have a local IP address, we get one by
calling ip_route(). */
if (ip_addr_isany(&(pcb->local_ip))) {
LWIP_ASSERT("tcp_output_segment: need to find route to host", 0);
}
/* Set retransmission timer running if it is not currently enabled */
if(pcb->rtime == -1) {
pcb->rtime = 0;
}
if (pcb->rttest == 0) {
pcb->rttest = tcp_ticks;
pcb->rtseq = seg->seqno;
LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_output_segment: rtseq %"U32_F"\n", pcb->rtseq));
}
LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output_segment: %"U32_F":%"U32_F"\n",
htonl(seg->tcphdr->seqno), htonl(seg->tcphdr->seqno) +
seg->len));
len = (u16_t)((u8_t *)seg->tcphdr - (u8_t *)seg->p->payload);
seg->p->len -= len;
seg->p->tot_len -= len;
seg->p->payload = seg->tcphdr;
seg->tcphdr->chksum = 0;
TCP_STATS_INC(tcp.xmit);
#if LWIP_NETIF_HWADDRHINT
ip_output_hinted(seg->p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos,
IP_PROTO_TCP, &(pcb->addr_hint));
#elif LWIP_3RD_PARTY_L3
pcb->ip_output(seg->p, pcb, seg->seqno < pcb->snd_nxt);
#else /* LWIP_NETIF_HWADDRHINT*/
ip_output(seg->p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos, IP_PROTO_TCP);
#endif /* LWIP_NETIF_HWADDRHINT*/
}
