Split TCP code out into proto/tcp.c

src/core/nic.c

@@ -219,7 +219,6 @@ static int rarp(void);
 #else
 static int bootp(void);
 #endif
-static unsigned short tcpudpchksum(struct iphdr *ip);
 
 
 /*
@@ -320,9 +319,6 @@ static int nic_load ( struct type_dev *type_dev,
 	char	*kernel;
 
 	/* Now use TFTP to load file */
-#ifdef	DOWNLOAD_PROTO_NFS
-	rpc_init();
-#endif
 	kernel = KERNEL_BUF[0] == '\0' ? 
 #ifdef	DEFAULT_BOOTFILE
 		DEFAULT_BOOTFILE
@@ -529,29 +525,6 @@ void build_udp_hdr(unsigned long destip,
 		udp->chksum = 0xffff;
 }
 
-#ifdef DOWNLOAD_PROTO_HTTP
-void build_tcp_hdr(unsigned long destip, unsigned int srcsock,
-		  unsigned int destsock, long send_seq, long recv_seq,
-		  int window, int flags, int ttl, int len, const void *buf)
-{
-       struct iphdr *ip;
-       struct tcphdr *tcp;
-       ip = (struct iphdr *)buf;
-       build_ip_hdr(destip, ttl, IP_TCP, 0, len, buf);
-       tcp = (struct tcphdr *)(ip + 1);
-       tcp->src = htons(srcsock);
-       tcp->dst = htons(destsock);
-       tcp->seq = htonl(send_seq);
-       tcp->ack = htonl(recv_seq);
-       tcp->ctrl = htons(flags + (5 << 12)); /* No TCP options */
-       tcp->window = htons(window);
-       tcp->chksum = 0;
-       if ((tcp->chksum = tcpudpchksum(ip)) == 0)
-	       tcp->chksum = 0xffff;
-}
-#endif
-
-
 /**************************************************************************
 UDP_TRANSMIT - Send an UDP datagram
 **************************************************************************/
@@ -562,37 +535,6 @@ int udp_transmit(unsigned long destip, unsigned int srcsock,
 	return ip_transmit(len, buf);
 }
 
-/**************************************************************************
-TCP_TRANSMIT - Send a TCP packet
-**************************************************************************/
-#ifdef DOWNLOAD_PROTO_HTTP
-int tcp_transmit(unsigned long destip, unsigned int srcsock,
-		unsigned int destsock, long send_seq, long recv_seq,
-		int window, int flags, int len, const void *buf)
-{
-       build_tcp_hdr(destip, srcsock, destsock, send_seq, recv_seq,
-		     window, flags, 60, len, buf);
-       return ip_transmit(len, buf);
-}
-
-int tcp_reset(struct iphdr *ip) {
-       struct tcphdr *tcp = (struct tcphdr *)(ip + 1);
-       char buf[sizeof(struct iphdr) + sizeof(struct tcphdr)];
-
-       if (!(tcp->ctrl & htons(RST))) {
-	      long seq = ntohl(tcp->seq) + ntohs(ip->len) -
-			 sizeof(struct iphdr) -
-			 ((ntohs(tcp->ctrl) >> 10) & 0x3C);
-	      if (tcp->ctrl & htons(SYN|FIN))
-		      seq++;
-	      return tcp_transmit(ntohl(ip->src.s_addr),
-				  ntohs(tcp->dst), ntohs(tcp->src),
-				  tcp->ctrl&htons(ACK) ? ntohl(tcp->ack) : 0,
-				  seq, TCP_MAX_WINDOW, RST, sizeof(buf), buf);
-       }
-       return (1);
-}
-#endif
 
 /**************************************************************************
 QDRAIN - clear the nic's receive queue
@@ -616,9 +558,6 @@ void rx_qdrain(void)
 	await_reply(await_qdrain, 0, NULL, 0);
 }
 
-#ifdef	DOWNLOAD_PROTO_TFTP
-#endif	/* DOWNLOAD_PROTO_TFTP */
-
 #ifdef	RARP_NOT_BOOTP
 /**************************************************************************
 RARP - Get my IP address and load information
@@ -876,7 +815,7 @@ static int bootp(void)
 }
 #endif	/* RARP_NOT_BOOTP */
 
-static uint16_t tcpudpchksum(struct iphdr *ip)
+uint16_t tcpudpchksum(struct iphdr *ip)
 {
 	struct udp_pseudo_hdr pseudo;
 	uint16_t checksum;
@@ -1034,239 +973,6 @@ void join_group(int slot, unsigned long group)
 
 #include "proto_eth_slow.c"
 
-/**************************************************************************
-TCP - Simple-minded TCP stack. Can only send data once and then
-      receive the response. The algorithm for computing window
-      sizes and delaying ack's is currently broken, and thus
-      disabled. Performance would probably improve a little, if
-      this gets fixed. FIXME
-**************************************************************************/
-#ifdef DOWNLOAD_PROTO_HTTP
-static int await_tcp(int ival, void *ptr, unsigned short ptype __unused,
-		    struct iphdr *ip, struct udphdr *udp __unused,
-		    struct tcphdr *tcp)
-{
-       if (!tcp) {
-	       return 0;
-       }
-       if (arptable[ARP_CLIENT].ipaddr.s_addr != ip->dest.s_addr)
-	       return 0;
-       if (ntohs(tcp->dst) != ival) {
-	       tcp_reset(ip);
-	       return 0;
-       }
-       *(void **)ptr = tcp;
-       return 1;
-}
-
-int tcp_transaction(unsigned long destip, unsigned int destsock, void *ptr,
-		   int (*send)(int len, void *buf, void *ptr),
-		   int (*recv)(int len, const void *buf, void *ptr)) {
-       static uint16_t srcsock = 0;
-       int	       rc = 1;
-       long	       send_seq = currticks();
-       long	       recv_seq = 0;
-       int	       can_send = 0;
-       int	       sent_all = 0;
-       struct iphdr   *ip;
-       struct tcphdr  *tcp;
-       int	       ctrl = SYN;
-       char	       buf[128]; /* Small outgoing buffer */
-       long	       payload;
-       int	       header_size;
-       int	       window = 3*TCP_MIN_WINDOW;
-       long	       last_ack = 0;
-       long	       last_sent = 0;
-       long	       rtt = 0;
-       long	       srtt = 0;
-       long	       rto = TCP_INITIAL_TIMEOUT;
-       int	       retry = TCP_MAX_TIMEOUT/TCP_INITIAL_TIMEOUT;
-       enum { CLOSED, SYN_RCVD, ESTABLISHED,
-	      FIN_WAIT_1, FIN_WAIT_2 } state = CLOSED;
-
-       if (!srcsock) {
-	       srcsock = currticks();
-       }
-       if (++srcsock < 1024)
-	       srcsock += 1024;
-
-       await_reply(await_qdrain, 0, NULL, 0);
-
- send_data:
-       if (ctrl & ACK)
-	       last_ack = recv_seq;
-       if (!tcp_transmit(destip, srcsock, destsock, send_seq,
-			 recv_seq, window, ctrl,
-			 sizeof(struct iphdr) + sizeof(struct tcphdr)+
-			 can_send, buf)) {
-	       return (0);
-       }
-       last_sent = currticks();
-
- recv_data:
-       if (!await_reply(await_tcp, srcsock, &tcp,
-			(state == ESTABLISHED && !can_send)
-			? TCP_MAX_TIMEOUT : rto)) {
-	       if (state == ESTABLISHED) {
- close:
-		       ctrl = FIN|ACK;
-		       state = FIN_WAIT_1;
-		       rc = 0;
-		       goto send_data;
-	       }
-
-	       if (state == FIN_WAIT_1 || state == FIN_WAIT_2)
-		       return (rc);
-
-	       if (--retry <= 0) {
-		       /* time out */
-		       if (state == SYN_RCVD) {
-			       tcp_transmit(destip, srcsock, destsock,
-					    send_seq, 0, window, RST,
-					    sizeof(struct iphdr) +
-					    sizeof(struct tcphdr), buf);
-		       }
-		       return (0);
-	       }
-	       /* retransmit */
-	       goto send_data;
-       }
- got_data:
-       retry = TCP_MAX_RETRY;
-
-       if (tcp->ctrl & htons(ACK) ) {
-	       char *data;
-	       int syn_ack, consumed;
-
-	       if (state == FIN_WAIT_1 || state == FIN_WAIT_2) {
-		       state = FIN_WAIT_2;
-		       ctrl = ACK;
-		       goto consume_data;
-	       }
-	       syn_ack = state == CLOSED || state == SYN_RCVD;
-	       consumed = ntohl(tcp->ack) - send_seq - syn_ack;
-	       if (consumed < 0 || consumed > can_send) {
-		       tcp_reset((struct iphdr *)&nic.packet[ETH_HLEN]);
-		       goto recv_data;
-	       }
-
-	       rtt = currticks() - last_sent;
-	       srtt = !srtt ? rtt : (srtt*4 + rtt)/5;
-	       rto = srtt + srtt/2;
-	       if (rto < TCP_MIN_TIMEOUT)
-		       rto = TCP_MIN_TIMEOUT;
-	       else if (rto > TCP_MAX_TIMEOUT)
-		       rto = TCP_MAX_TIMEOUT;
-
-	       can_send -= consumed;
-	       send_seq += consumed + syn_ack;
-	       data = buf + sizeof(struct iphdr) + sizeof(struct tcphdr);
-	       if (can_send) {
-		       memmove(data, data + consumed, can_send);
-	       }
-	       if (!sent_all) {
-		       int more_data;
-		       data += can_send;
-		       more_data = buf + sizeof(buf) - data;
-		       if (more_data > 0) {
-			       more_data = send(more_data, data, ptr);
-			       can_send += more_data;
-		       }
-		       sent_all = !more_data;
-	       }
-	       if (state == SYN_RCVD) {
-		       state = ESTABLISHED;
-		       ctrl = PSH|ACK;
-		       goto consume_data;
-	       }
-	       if (tcp->ctrl & htons(RST))
-		       return (0);
-       } else if (tcp->ctrl & htons(RST)) {
-	       if (state == CLOSED)
-		       goto recv_data;
-	       return (0);
-       }
-
- consume_data:
-       ip  = (struct iphdr *)&nic.packet[ETH_HLEN];
-       header_size = sizeof(struct iphdr) + ((ntohs(tcp->ctrl)>>10)&0x3C);
-       payload = ntohs(ip->len) - header_size;
-       if (payload > 0 && state == ESTABLISHED) {
-	       int old_bytes = recv_seq - (long)ntohl(tcp->seq);
-	       if (old_bytes >= 0 && payload - old_bytes > 0) {
-		       recv_seq += payload - old_bytes;
-		       if (state != FIN_WAIT_1 && state != FIN_WAIT_2 &&
-			   !recv(payload - old_bytes,
-				 &nic.packet[ETH_HLEN+header_size+old_bytes],
-				 ptr)) {
-			       goto close;
-		       }
-		       if ((state == ESTABLISHED || state == SYN_RCVD) &&
-			   !(tcp->ctrl & htons(FIN))) {
-			       int in_window = window - 2*TCP_MIN_WINDOW >
-						recv_seq - last_ack;
-			       ctrl = can_send ? PSH|ACK : ACK;
-			       if (!can_send && in_window) {
-/* Window scaling is broken right now, just fall back to acknowledging every */
-/* packet immediately and unconditionally. FIXME		       */ /***/
-/*				       if (await_reply(await_tcp, srcsock,
-						       &tcp, rto))
-					       goto got_data;
-				       else */
-					       goto send_data;
-			       }
-			       if (!in_window) {
-				       window += TCP_MIN_WINDOW;
-				       if (window > TCP_MAX_WINDOW)
-					       window = TCP_MAX_WINDOW;
-			       }
-			       goto send_data;
-		       }
-	       } else {
-		       /* saw old data again, must have lost packets */
-		       window /= 2;
-		       if (window < 2*TCP_MIN_WINDOW)
-			       window = 2*TCP_MIN_WINDOW;
-	       }
-       }
-
-       if (tcp->ctrl & htons(FIN)) {
-	       if (state == ESTABLISHED) {
-		       ctrl = FIN|ACK;
-	       } else if (state == FIN_WAIT_1 || state == FIN_WAIT_2) {
-		       ctrl = ACK;
-	       } else {
-		       ctrl = RST;
-	       }
-	       return (tcp_transmit(destip, srcsock, destsock,
-				    send_seq, recv_seq + 1, window, ctrl,
-				    sizeof(struct iphdr) +
-				    sizeof(struct tcphdr), buf) &&
-		       (state == ESTABLISHED ||
-			state == FIN_WAIT_1 || state == FIN_WAIT_2) &&
-		       !can_send);
-       }
-
-       if (state == CLOSED) {
-	       if (tcp->ctrl & htons(SYN)) {
-		       recv_seq = ntohl(tcp->seq) + 1;
-		       if (!(tcp->ctrl & htons(ACK))) {
-			       state = SYN_RCVD;
-			       ctrl = SYN|ACK|PSH;
-			       goto send_data;
-		       } else {
-			       state = ESTABLISHED;
-			       ctrl = PSH|ACK;
-		       }
-	       }
-       }
-
-       if (can_send || payload) {
-	       goto send_data;
-       }
-       goto recv_data;
-}
-#endif
 
 /**************************************************************************
 AWAIT_REPLY - Wait until we get a response for our request
@@ -1361,7 +1067,6 @@ int await_reply(reply_t reply, int ival, void *ptr, long timeout)
 			}
 		}
 		tcp = 0;
-#ifdef DOWNLOAD_PROTO_HTTP
 		if (ip && (ip->protocol == IP_TCP) &&
 		    (nic.packetlen >=
 		     ETH_HLEN + sizeof(struct iphdr) + sizeof(struct tcphdr))){
@@ -1377,7 +1082,6 @@ int await_reply(reply_t reply, int ival, void *ptr, long timeout)
 			}
 
 		}
-#endif
 		result = reply(ival, ptr, ptype, ip, udp, tcp);
 		if (result > 0) {
 			return result;

src/include/ip.h

@@ -18,4 +18,6 @@ struct iphdr {
 	struct in_addr dest;
 } PACKED;
 
+extern uint16_t tcpudpchksum(struct iphdr *ip);
+
 #endif	/* _IP_H */

src/include/tcp.h

@@ -9,10 +9,6 @@
 #define TCP_MIN_WINDOW          (1500-TCP_MAX_HEADER)
 #define TCP_MAX_WINDOW          (65535-TCP_MAX_HEADER)
 
-
-#define MAX_URL                 80
-
-
 #define FIN             1
 #define SYN             2
 #define RST             4
@@ -32,4 +28,10 @@ struct tcphdr {
        uint16_t urgent;
 };
 
+extern int tcp_transaction ( unsigned long destip, unsigned int destsock,
+			     void *ptr,
+			     int (*send)(int len, void *buf, void *ptr),
+			     int (*recv)(int len, const void *buf, void *ptr));
+
+
 #endif	/* _TCP_H */

src/proto/tcp.c

@@ -0,0 +1,286 @@
+#include "etherboot.h"
+#include "ip.h"
+#include "tcp.h"
+
+
+void build_tcp_hdr(unsigned long destip, unsigned int srcsock,
+		  unsigned int destsock, long send_seq, long recv_seq,
+		  int window, int flags, int ttl, int len, const void *buf)
+{
+       struct iphdr *ip;
+       struct tcphdr *tcp;
+       ip = (struct iphdr *)buf;
+       build_ip_hdr(destip, ttl, IP_TCP, 0, len, buf);
+       tcp = (struct tcphdr *)(ip + 1);
+       tcp->src = htons(srcsock);
+       tcp->dst = htons(destsock);
+       tcp->seq = htonl(send_seq);
+       tcp->ack = htonl(recv_seq);
+       tcp->ctrl = htons(flags + (5 << 12)); /* No TCP options */
+       tcp->window = htons(window);
+       tcp->chksum = 0;
+       if ((tcp->chksum = tcpudpchksum(ip)) == 0)
+	       tcp->chksum = 0xffff;
+}
+
+/**************************************************************************
+TCP_TRANSMIT - Send a TCP packet
+**************************************************************************/
+int tcp_transmit(unsigned long destip, unsigned int srcsock,
+		unsigned int destsock, long send_seq, long recv_seq,
+		int window, int flags, int len, const void *buf)
+{
+       build_tcp_hdr(destip, srcsock, destsock, send_seq, recv_seq,
+		     window, flags, 60, len, buf);
+       return ip_transmit(len, buf);
+}
+
+int tcp_reset(struct iphdr *ip) {
+       struct tcphdr *tcp = (struct tcphdr *)(ip + 1);
+       char buf[sizeof(struct iphdr) + sizeof(struct tcphdr)];
+
+       if (!(tcp->ctrl & htons(RST))) {
+	      long seq = ntohl(tcp->seq) + ntohs(ip->len) -
+			 sizeof(struct iphdr) -
+			 ((ntohs(tcp->ctrl) >> 10) & 0x3C);
+	      if (tcp->ctrl & htons(SYN|FIN))
+		      seq++;
+	      return tcp_transmit(ntohl(ip->src.s_addr),
+				  ntohs(tcp->dst), ntohs(tcp->src),
+				  tcp->ctrl&htons(ACK) ? ntohl(tcp->ack) : 0,
+				  seq, TCP_MAX_WINDOW, RST, sizeof(buf), buf);
+       }
+       return (1);
+}
+
+/**************************************************************************
+TCP - Simple-minded TCP stack. Can only send data once and then
+      receive the response. The algorithm for computing window
+      sizes and delaying ack's is currently broken, and thus
+      disabled. Performance would probably improve a little, if
+      this gets fixed. FIXME
+**************************************************************************/
+static int await_tcp(int ival, void *ptr, unsigned short ptype __unused,
+		    struct iphdr *ip, struct udphdr *udp __unused,
+		    struct tcphdr *tcp)
+{
+       if (!tcp) {
+	       return 0;
+       }
+       if (arptable[ARP_CLIENT].ipaddr.s_addr != ip->dest.s_addr)
+	       return 0;
+       if (ntohs(tcp->dst) != ival) {
+	       tcp_reset(ip);
+	       return 0;
+       }
+       *(void **)ptr = tcp;
+       return 1;
+}
+
+int tcp_transaction(unsigned long destip, unsigned int destsock, void *ptr,
+		   int (*send)(int len, void *buf, void *ptr),
+		   int (*recv)(int len, const void *buf, void *ptr)) {
+       static uint16_t srcsock = 0;
+       int	       rc = 1;
+       long	       send_seq = currticks();
+       long	       recv_seq = 0;
+       int	       can_send = 0;
+       int	       sent_all = 0;
+       struct iphdr   *ip;
+       struct tcphdr  *tcp;
+       int	       ctrl = SYN;
+       char	       buf[128]; /* Small outgoing buffer */
+       long	       payload;
+       int	       header_size;
+       int	       window = 3*TCP_MIN_WINDOW;
+       long	       last_ack = 0;
+       long	       last_sent = 0;
+       long	       rtt = 0;
+       long	       srtt = 0;
+       long	       rto = TCP_INITIAL_TIMEOUT;
+       int	       retry = TCP_MAX_TIMEOUT/TCP_INITIAL_TIMEOUT;
+       enum { CLOSED, SYN_RCVD, ESTABLISHED,
+	      FIN_WAIT_1, FIN_WAIT_2 } state = CLOSED;
+
+       if (!srcsock) {
+	       srcsock = currticks();
+       }
+       if (++srcsock < 1024)
+	       srcsock += 1024;
+
+       rx_qdrain();
+
+ send_data:
+       if (ctrl & ACK)
+	       last_ack = recv_seq;
+       if (!tcp_transmit(destip, srcsock, destsock, send_seq,
+			 recv_seq, window, ctrl,
+			 sizeof(struct iphdr) + sizeof(struct tcphdr)+
+			 can_send, buf)) {
+	       return (0);
+       }
+       last_sent = currticks();
+
+ recv_data:
+       if (!await_reply(await_tcp, srcsock, &tcp,
+			(state == ESTABLISHED && !can_send)
+			? TCP_MAX_TIMEOUT : rto)) {
+	       if (state == ESTABLISHED) {
+ close:
+		       ctrl = FIN|ACK;
+		       state = FIN_WAIT_1;
+		       rc = 0;
+		       goto send_data;
+	       }
+
+	       if (state == FIN_WAIT_1 || state == FIN_WAIT_2)
+		       return (rc);
+
+	       if (--retry <= 0) {
+		       /* time out */
+		       if (state == SYN_RCVD) {
+			       tcp_transmit(destip, srcsock, destsock,
+					    send_seq, 0, window, RST,
+					    sizeof(struct iphdr) +
+					    sizeof(struct tcphdr), buf);
+		       }
+		       return (0);
+	       }
+	       /* retransmit */
+	       goto send_data;
+       }
+       /* got_data: */
+       retry = TCP_MAX_RETRY;
+
+       if (tcp->ctrl & htons(ACK) ) {
+	       char *data;
+	       int syn_ack, consumed;
+
+	       if (state == FIN_WAIT_1 || state == FIN_WAIT_2) {
+		       state = FIN_WAIT_2;
+		       ctrl = ACK;
+		       goto consume_data;
+	       }
+	       syn_ack = state == CLOSED || state == SYN_RCVD;
+	       consumed = ntohl(tcp->ack) - send_seq - syn_ack;
+	       if (consumed < 0 || consumed > can_send) {
+		       tcp_reset((struct iphdr *)&nic.packet[ETH_HLEN]);
+		       goto recv_data;
+	       }
+
+	       rtt = currticks() - last_sent;
+	       srtt = !srtt ? rtt : (srtt*4 + rtt)/5;
+	       rto = srtt + srtt/2;
+	       if (rto < TCP_MIN_TIMEOUT)
+		       rto = TCP_MIN_TIMEOUT;
+	       else if (rto > TCP_MAX_TIMEOUT)
+		       rto = TCP_MAX_TIMEOUT;
+
+	       can_send -= consumed;
+	       send_seq += consumed + syn_ack;
+	       data = buf + sizeof(struct iphdr) + sizeof(struct tcphdr);
+	       if (can_send) {
+		       memmove(data, data + consumed, can_send);
+	       }
+	       if (!sent_all) {
+		       int more_data;
+		       data += can_send;
+		       more_data = buf + sizeof(buf) - data;
+		       if (more_data > 0) {
+			       more_data = send(more_data, data, ptr);
+			       can_send += more_data;
+		       }
+		       sent_all = !more_data;
+	       }
+	       if (state == SYN_RCVD) {
+		       state = ESTABLISHED;
+		       ctrl = PSH|ACK;
+		       goto consume_data;
+	       }
+	       if (tcp->ctrl & htons(RST))
+		       return (0);
+       } else if (tcp->ctrl & htons(RST)) {
+	       if (state == CLOSED)
+		       goto recv_data;
+	       return (0);
+       }
+
+ consume_data:
+       ip  = (struct iphdr *)&nic.packet[ETH_HLEN];
+       header_size = sizeof(struct iphdr) + ((ntohs(tcp->ctrl)>>10)&0x3C);
+       payload = ntohs(ip->len) - header_size;
+       if (payload > 0 && state == ESTABLISHED) {
+	       int old_bytes = recv_seq - (long)ntohl(tcp->seq);
+	       if (old_bytes >= 0 && payload - old_bytes > 0) {
+		       recv_seq += payload - old_bytes;
+		       if (state != FIN_WAIT_1 && state != FIN_WAIT_2 &&
+			   !recv(payload - old_bytes,
+				 &nic.packet[ETH_HLEN+header_size+old_bytes],
+				 ptr)) {
+			       goto close;
+		       }
+		       if ((state == ESTABLISHED || state == SYN_RCVD) &&
+			   !(tcp->ctrl & htons(FIN))) {
+			       int in_window = window - 2*TCP_MIN_WINDOW >
+						recv_seq - last_ack;
+			       ctrl = can_send ? PSH|ACK : ACK;
+			       if (!can_send && in_window) {
+/* Window scaling is broken right now, just fall back to acknowledging every */
+/* packet immediately and unconditionally. FIXME		       */ /***/
+/*				       if (await_reply(await_tcp, srcsock,
+						       &tcp, rto))
+					       goto got_data;
+				       else */
+					       goto send_data;
+			       }
+			       if (!in_window) {
+				       window += TCP_MIN_WINDOW;
+				       if (window > TCP_MAX_WINDOW)
+					       window = TCP_MAX_WINDOW;
+			       }
+			       goto send_data;
+		       }
+	       } else {
+		       /* saw old data again, must have lost packets */
+		       window /= 2;
+		       if (window < 2*TCP_MIN_WINDOW)
+			       window = 2*TCP_MIN_WINDOW;
+	       }
+       }
+
+       if (tcp->ctrl & htons(FIN)) {
+	       if (state == ESTABLISHED) {
+		       ctrl = FIN|ACK;
+	       } else if (state == FIN_WAIT_1 || state == FIN_WAIT_2) {
+		       ctrl = ACK;
+	       } else {
+		       ctrl = RST;
+	       }
+	       return (tcp_transmit(destip, srcsock, destsock,
+				    send_seq, recv_seq + 1, window, ctrl,
+				    sizeof(struct iphdr) +
+				    sizeof(struct tcphdr), buf) &&
+		       (state == ESTABLISHED ||
+			state == FIN_WAIT_1 || state == FIN_WAIT_2) &&
+		       !can_send);
+       }
+
+       if (state == CLOSED) {
+	       if (tcp->ctrl & htons(SYN)) {
+		       recv_seq = ntohl(tcp->seq) + 1;
+		       if (!(tcp->ctrl & htons(ACK))) {
+			       state = SYN_RCVD;
+			       ctrl = SYN|ACK|PSH;
+			       goto send_data;
+		       } else {
+			       state = ESTABLISHED;
+			       ctrl = PSH|ACK;
+		       }
+	       }
+       }
+
+       if (can_send || payload) {
+	       goto send_data;
+       }
+       goto recv_data;
+}