2.4.0-ac3 write() to tcp socket returning errno of -3 (ESRCH: "No such process")

diff -ru linux-2.4.0-ac3/net/ipv4/tcp.c linux-2.4.0-ac3-debugging/net/ipv4/tcp.c
@@ -451,6 +451,23 @@
 
 #define TCP_PAGES(amt) (((amt)+TCP_MEM_QUANTUM-1)/TCP_MEM_QUANTUM)
 
+#define CHECK_TCP_RET() check_tcp_ret(err, __FILE__, __LINE__, __FUNCTION__)
+
+void check_tcp_ret(int ret, char *file, int line, char *func) {
+  if(ret < 0) {
+	switch(-ret) {
+	  case EAGAIN: case EBADF: case EPIPE: case ENOSPC: case EIO: case ECONNRESET:
+	  case EINTR: case ETIMEDOUT: case EFAULT: case EINVAL: case EMSGSIZE: case ENOMEM:
+	  case ENOBUFS: case ENOTCONN: case ECONNREFUSED: case ERESTARTSYS: case EHOSTUNREACH:
+		break;
+
+	  default:
+		printk(KERN_ERR "%s:%d:%s: err is unexpectedly %d.\n", file, line, func, ret);
+	}
+  }
+}
+
+
 int tcp_mem_schedule(struct sock *sk, int size, int kind)
 {
 	int amt = TCP_PAGES(size);

@@ -883,6 +900,8 @@
 	}
 	current->state = TASK_RUNNING;
 	remove_wait_queue(sk->sleep, &wait);
+	if(timeo < 0)
+	  printk(KERN_ERR "wait_for_tcp_memory: timeo == %ld\n", timeo);
 	return timeo;
 }
 

@@ -916,8 +935,10 @@
 
 	/* Wait for a connection to finish. */
 	if ((1 << sk->state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
-		if((err = wait_for_tcp_connect(sk, flags, &timeo)) != 0)
-			goto out_unlock;
+	  if((err = wait_for_tcp_connect(sk, flags, &timeo)) != 0) {
+		CHECK_TCP_RET();
+		goto out_unlock;
+	  }
 
 	/* This should be in poll */
 	clear_bit(SOCK_ASYNC_NOSPACE, &sk->socket->flags);

@@ -938,8 +959,11 @@
 		while (seglen > 0) {
 			int copy, tmp, queue_it;
 
-			if (err)
-				goto do_fault2;
+			if (err) {
+			  if(copied) check_tcp_ret(copied, __FILE__, __LINE__, __FUNCTION__);
+			  else CHECK_TCP_RET();
+			  goto do_fault2;
+			}
 
 			/* Stop on errors. */
 			if (sk->err)

@@ -948,7 +972,7 @@
 			/* Make sure that we are established. */
 			if (sk->shutdown & SEND_SHUTDOWN)
 				goto do_shutdown;
-	
+
 			/* Now we need to check if we have a half
 			 * built packet we can tack some data onto.
 			 */

@@ -964,6 +988,7 @@
 						copy = skb_tailroom(skb);
 					if(copy > seglen)
 						copy = seglen;
+					if(copy < 0) printk(KERN_ERR "tcp_sendmsg:%d: copy = %d, mss_now = %d, skb->len = %d, skb_tailroom(skb) = %d, seglen = %d.\n", __LINE__ copy, mss_now, skb->len, skb_tailroom(skb), seglen);
 					if(last_byte_was_odd) {
 						if(copy_from_user(skb_put(skb, copy),
 								  from, copy))

@@ -975,6 +1000,7 @@
 							csum_and_copy_from_user(
 							from, skb_put(skb, copy),
 							copy, skb->csum, &err);
+						CHECK_TCP_RET();
 					}
 					/*
 					 * FIXME: the *_user functions should

@@ -1042,6 +1068,7 @@
 				}
 				if (signal_pending(current)) {
 					err = sock_intr_errno(timeo);
+			  CHECK_TCP_RET();
 					goto do_interrupted;
 				}
 				timeo = wait_for_tcp_memory(sk, timeo);

@@ -1078,8 +1105,11 @@
 			skb->csum = csum_and_copy_from_user(from,
 					skb_put(skb, copy), copy, 0, &err);
 
-			if (err)
-				goto do_fault;
+			if (err) {
+			  if(copied) check_tcp_ret(copied, __FILE__, __LINE__, __FUNCTION__);
+			  else CHECK_TCP_RET();
+			  goto do_fault;
+			}
 
 			from += copy;
 			copied += copy;

@@ -1092,6 +1122,7 @@
 		}
 	}
 	err = copied;
+			  CHECK_TCP_RET();
 out:
 	__tcp_push_pending_frames(sk, tp, mss_now, tp->nonagle);
 out_unlock:

@@ -1100,14 +1131,20 @@
 	return err;
 
 do_sock_err:
-	if (copied)
+	if (copied) {
 		err = copied;
-	else
+		CHECK_TCP_RET();
+
+	} else {
 		err = sock_error(sk);
+		CHECK_TCP_RET();
+	}
 	goto out;
 do_shutdown:
-	if (copied)
+	if (copied) {
 		err = copied;
+		CHECK_TCP_RET();
+	}
 	else {
 		if (!(flags&MSG_NOSIGNAL))
 			send_sig(SIGPIPE, current, 0);

@@ -1115,14 +1152,18 @@
 	}
 	goto out;
 do_interrupted:
-	if (copied)
+	if (copied) {
 		err = copied;
+		CHECK_TCP_RET();
+	}
 	goto out_unlock;
 do_fault:
 	__kfree_skb(skb);
 do_fault2:
-	if (copied)
+	if (copied) {
 		err = copied;
+		CHECK_TCP_RET();
+	}
 	else
 		err = -EFAULT;
 	goto out;

@@ -1283,6 +1324,8 @@
 
 	remove_wait_queue(sk->sleep, &wait);
 	__set_current_state(TASK_RUNNING);
+	if(timeo < 0)
+	  printk(KERN_ERR "tcp_data_wait: timeo == %ld.\n", timeo);
 	return timeo;
 }
 

@@ -2026,8 +2069,10 @@
 		if (sk->state != TCP_LISTEN)
 			break;
 		err = sock_intr_errno(timeo);
-		if (signal_pending(current))
+		if (signal_pending(current)) {
+  		    CHECK_TCP_RET();
 			break;
+		}
 		err = -EAGAIN;
 		if (!timeo)
 			break;

diff -u --recursive --new-file v2.4.0/linux/net/ipv4/tcp.c linux/net/ipv4/tcp.c
@@ -954,7 +954,7 @@
 			 */
 			skb = sk->write_queue.prev;
 			if (tp->send_head &&
-			    (mss_now - skb->len) > 0) {
+			    (mss_now > skb->len)) {
 				copy = skb->len;
 				if (skb_tailroom(skb) > 0) {
 					int last_byte_was_odd = (copy % 4);