/*!
* \brief Send a UDP packet.
*
* \param sock Socket descriptor. This pointer must have been
* retrieved by calling NutUdpCreateSocket().
* \param daddr IP address of the remote host in network byte order.
* \param port Remote port number in host byte order.
* \param nb Network buffer structure containing the datagram.
* This buffer will be released if the function returns
* an error.
*
* \note Applications typically do not call this function but
* use the UDP socket interface.
*
* \return 0 on success, -1 otherwise.
*/
int NutUdpOutput(UDPSOCKET * sock, uint32_t daddr, uint16_t port, NETBUF * nb)
{
uint32_t saddr;
uint32_t csum;
UDPHDR *uh;
NUTDEVICE *dev;
IFNET *nif;
if ((nb = NutNetBufAlloc(nb, NBAF_TRANSPORT, sizeof(UDPHDR))) == 0)
return -1;
uh = nb->nb_tp.vp;
uh->uh_sport = sock->so_local_port;
uh->uh_dport = htons(port);
uh->uh_ulen = htons((uint16_t)(nb->nb_tp.sz + nb->nb_ap.sz));
/*
* Get local address for this destination.
*/
if ((dev = NutIpRouteQuery(daddr, &saddr)) != 0) {
nif = dev->dev_icb;
saddr = nif->if_local_ip;
} else
saddr = 0;
uh->uh_sum = 0;
csum = NutIpPseudoChkSumPartial(saddr, daddr, IPPROTO_UDP, uh->uh_ulen);
csum = NutIpChkSumPartial(csum, uh, sizeof(UDPHDR));
uh->uh_sum = NutIpChkSum(csum, nb->nb_ap.vp, nb->nb_ap.sz);
return NutIpOutput(IPPROTO_UDP, daddr, nb);
}
/*!
* \brief Reject an incoming segment.
*
* Send RST in response to an incoming segment, which should
* be rejected.
*
* The function avoids to send out a RST segment in response to
* an incoming RST segment.
*
* \note This function is mainly used by the TCP state machine.
* Applications typically do not call this function.
*
* \param nb Network buffer structure of the incoming segment.
* Will be released within this function.
*
* \return 0 on success, -1 otherwise.
*/
int NutTcpReject(NETBUF * nb)
{
u_short csum;
IPHDR *ih = (IPHDR *) nb->nb_nw.vp;
TCPHDR *th = (TCPHDR *) nb->nb_tp.vp;
/*
* Never send RST in response to RST.
*/
if (th->th_flags & TH_RST) {
NutNetBufFree(nb);
return 0;
}
/*
* Remove any application data and TCP header options.
*/
nb->nb_ap.sz = 0;
nb->nb_tp.sz = sizeof(TCPHDR);
/*
* Swap ports.
*/
csum = th->th_sport;
th->th_sport = th->th_dport;
th->th_dport = csum;
/*
* If the incoming segment has an ACK field, the reset
* takes its sequence number from the ACK field of the
* segment, otherwise the reset has sequence number zero
* and the ACK field is set to the sum of the sequence
* number and segment length of the incoming segment.
*/
if (th->th_flags & TH_ACK) {
th->th_flags = TH_RST;
th->th_seq = th->th_ack;
th->th_ack = 0;
} else {
if (th->th_flags & TH_SYN)
th->th_ack = htonl(ntohl(th->th_seq) + 1);
else
th->th_ack = th->th_seq;
th->th_seq = 0;
th->th_flags = TH_RST | TH_ACK;
}
th->th_x2 = 0;
th->th_off = sizeof(TCPHDR) / 4;
th->th_win = 0;
th->th_urp = 0;
/*
* Calculate TCP checksum without application data.
*/
th->th_sum = 0;
csum =
NutIpPseudoChkSumPartial(ih->ip_dst, ih->ip_src, IPPROTO_TCP,
htons(nb->nb_tp.sz));
th->th_sum = NutIpChkSum(csum, th, nb->nb_tp.sz);
/*
* Sent segment back to the source.
*/
#ifdef NUTDEBUG
if (__tcp_trf)
NutDumpTcpHeader(__tcp_trs, "REJ", 0, nb);
#endif
if(NutIpOutput(IPPROTO_TCP, ih->ip_src, nb) == 0)
NutNetBufFree(nb);
return 0;
}
/*!
* \brief Initiate TCP segment transmission.
*
* Check the TCP socket status and send any segment waiting
* for transmission.
*
* The function will not return until the data has been stored in the
* network device hardware for transmission. If the device is not ready
* for transmitting a new packet, the calling thread will be suspended
* until the device becomes ready again.
*
* If the target host is connected through an Ethernet network and if
* the hardware address of that host is currently unknown, an ARP
* request is sent out and the function will block until a response
* is received or an ARP timeout occurs.
*
* Segments containing data or SYN and FIN flags are added to a special
* queue for unacknowledged segments and will be retransmitted by the
* TCP timer thread, if not acknowledged by the remote within a specific
* time. The state machine will remove these segments from the queue
* as soon as they are acknowledged.
*
* \note This function is mainly used by the TCP state machine.
* Applications typically do not call this function but
* use NutTcpSend(), which is part of the TCP socket interface.
*
* \param sock Socket descriptor. This pointer must have been retrieved
* by calling NutTcpCreateSocket().
* \param data Pointer to TCP segment contents.
* \param size TCP segment length.
*
* \return 0 on success, -1 otherwise. Returning 0 does not imply that
* the data has been successfully delivered, because flow control
* and retransmission is still handled in the background.
*/
int NutTcpOutput(TCPSOCKET * sock, CONST u_char * data, u_short size)
{
NETBUF *nb;
NETBUF *nb_clone = 0;
TCPHDR *th;
u_short csum;
u_char hlen;
/*
* Check if anything to send at all.
*/
if (size == 0
&& (sock->so_tx_flags & (SO_SYN | SO_FIN | SO_FORCE)) == 0)
return 0;
/*
* Build TCP header. Add room for MAXSEG option if this is a
* SYN segment.
*/
hlen = sizeof(TCPHDR);
if (sock->so_tx_flags & SO_SYN)
hlen += 4;
if ((nb = NutNetBufAlloc(0, NBAF_TRANSPORT, hlen)) == 0) {
sock->so_last_error = ENOBUFS;
return -1;
}
th = (TCPHDR *) nb->nb_tp.vp;
th->th_sport = sock->so_local_port;
th->th_dport = sock->so_remote_port;
th->th_x2 = 0;
th->th_off = hlen >> 2;
sock->so_tx_flags &= ~SO_FORCE;
/*
* Process ACK flag.
*/
th->th_seq = htonl(sock->so_tx_nxt);
if (sock->so_tx_flags & SO_ACK) {
th->th_flags = TH_ACK;
sock->so_tx_flags &= ~SO_ACK;
th->th_ack = htonl(sock->so_rx_nxt);
} else {
th->th_flags = 0;
th->th_ack = 0;
}
/*
* Any SYN is sent first. Add options too. We rely on the caller
* not to send a SYN segment with data, because this may break
* some old stacks.
*/
if (sock->so_tx_flags & SO_SYN) {
u_char *cp;
u_short n_mss = htons(sock->so_mss);
th->th_flags |= TH_SYN;
sock->so_tx_flags &= ~SO_SYN;
sock->so_tx_nxt++;
cp = (u_char *) (th + 1);
*cp++ = TCPOPT_MAXSEG;
*cp++ = TCPOLEN_MAXSEG;
*cp++ = *(u_char *)&n_mss;
*cp = *((u_char *)(&n_mss) + 1);
}
/*
* Next preference is sending data. Set PUSH flag.
*/
else if (size) {
if ((nb = NutNetBufAlloc(nb, NBAF_APPLICATION, size)) == 0) {
sock->so_last_error = ENOBUFS;
return -1;
}
memcpy(nb->nb_ap.vp, (void *)data, size);
sock->so_tx_nxt += size;
th->th_flags |= TH_PUSH;
}
/*
* If all data sent, transmit any waiting FIN.
*/
else if (sock->so_tx_flags & SO_FIN) {
th->th_flags |= TH_FIN;
sock->so_tx_flags &= ~SO_FIN;
sock->so_tx_nxt++;
//@@@printf ("[%04X]TcpOutput: sending FIN\n", (u_short) sock);
}
/*
* We close our receiver window, if it is
* below the maximum segment size.
*/
if (sock->so_rx_win < sock->so_mss)
th->th_win = 0;
else
th->th_win = htons(sock->so_rx_win);
th->th_sum = 0;
th->th_urp = 0;
/*
* Calculate TCP checksum.
*/
csum =
NutIpPseudoChkSumPartial(sock->so_local_addr, sock->so_remote_addr,
IPPROTO_TCP,
htons(nb->nb_tp.sz + nb->nb_ap.sz));
csum = NutIpChkSumPartial(csum, th, nb->nb_tp.sz);
th->th_sum = NutIpChkSum(csum, nb->nb_ap.vp, nb->nb_ap.sz);
#ifdef NUTDEBUG
if (__tcp_trf)
NutDumpTcpHeader(__tcp_trs, "OUT", sock, nb);
#endif
/*
* To avoid a race condition in tcp state machine, the segment is first
* appended to the transmission que, and then sent to the network.
*/
/*
* Append the segment to our transmission queue.
*/
//@@@printf ("[%04X]TcpOutput: size: %u, flags: %u\n", (u_short) sock, size, th->th_flags);
if (size || ((th->th_flags & (TH_FIN | TH_SYN)))) {
//@@@printf ("[%04X]TcpOutput: appending nb to queue\n", (u_short) sock);
NETBUF *nbp;
nb->nb_next = 0;
if ((nbp = sock->so_tx_nbq) == 0) {
sock->so_tx_nbq = nb;
/*
* First entry, so initialize our retransmission timer.
* It is also set at various places in the state machine,
* but here is the best central point to do it. We may
* carefully check later, if we can remove some in the
* state machine.
*/
sock->so_retran_time = (u_short) NutGetMillis() | 1;
}
else {
while (nbp->nb_next)
nbp = nbp->nb_next;
nbp->nb_next = nb;
}
if (sock->so_rtt_seq == 0)
sock->so_rtt_seq = ntohl (th->th_seq);
nb_clone = NutNetBufClone (nb);
}
else
nb_clone = nb;
/*
* IP output might fail because of routing, ARP or network device
* problems or because the system ran out of memory.
*/
if (NutIpOutput(IPPROTO_TCP, sock->so_remote_addr, nb_clone))
return -1;
NutNetBufFree (nb_clone);
return 0;
}