xref: /mOS-networking-stack/core/src/tcp_out.c (revision 91df013f)
1 #include <unistd.h>
2 #include <string.h>
3 
4 #include "tcp_out.h"
5 #include "mtcp.h"
6 #include "ip_in.h"
7 #include "ip_out.h"
8 #include "tcp_in.h"
9 #include "tcp.h"
10 #include "tcp_stream.h"
11 #include "eventpoll.h"
12 #include "timer.h"
13 #include "debug.h"
14 #include "config.h"
15 
16 #define TCP_CALCULATE_CHECKSUM		TRUE
17 #define ACK_PIGGYBACK			TRUE
18 /* Enable this for higher concurrency rate experiments */
19 #define TRY_SEND_BEFORE_QUEUE		/*FALSE*/ TRUE
20 
21 #define TCP_MAX_WINDOW 65535
22 
23 #define MAX(a, b) ((a)>(b)?(a):(b))
24 #define MIN(a, b) ((a)<(b)?(a):(b))
25 
26 extern struct pkt_info *
27 ClonePacketCtx(struct pkt_info *to, unsigned char *frame, struct pkt_ctx *from);
28 
29 /*----------------------------------------------------------------------------*/
30 static inline uint16_t
31 CalculateOptionLength(uint8_t flags)
32 {
33 	uint16_t optlen = 0;
34 
35 	if (flags & TCP_FLAG_SYN) {
36 		optlen += TCP_OPT_MSS_LEN;
37 #if TCP_OPT_SACK_ENABLED
38 		optlen += TCP_OPT_SACK_PERMIT_LEN;
39 #if !TCP_OPT_TIMESTAMP_ENABLED
40 		optlen += 2;	// insert NOP padding
41 #endif /* TCP_OPT_TIMESTAMP_ENABLED */
42 #endif /* TCP_OPT_SACK_ENABLED */
43 
44 #if TCP_OPT_TIMESTAMP_ENABLED
45 		optlen += TCP_OPT_TIMESTAMP_LEN;
46 #if !TCP_OPT_SACK_ENABLED
47 		optlen += 2;	// insert NOP padding
48 #endif /* TCP_OPT_SACK_ENABLED */
49 #endif /* TCP_OPT_TIMESTAMP_ENABLED */
50 
51 		optlen += TCP_OPT_WSCALE_LEN + 1;
52 
53 	} else {
54 
55 #if TCP_OPT_TIMESTAMP_ENABLED
56 		optlen += TCP_OPT_TIMESTAMP_LEN + 2;
57 #endif
58 
59 #if TCP_OPT_SACK_ENABLED
60 		if (flags & TCP_FLAG_SACK) {
61 			optlen += TCP_OPT_SACK_LEN + 2;
62 		}
63 #endif
64 	}
65 
66 	assert(optlen % 4 == 0);
67 
68 	return optlen;
69 }
70 /*----------------------------------------------------------------------------*/
71 static inline void
72 GenerateTCPTimestamp(tcp_stream *cur_stream, uint8_t *tcpopt, uint32_t cur_ts)
73 {
74 	uint32_t *ts = (uint32_t *)(tcpopt + 2);
75 
76 	tcpopt[0] = TCP_OPT_TIMESTAMP;
77 	tcpopt[1] = TCP_OPT_TIMESTAMP_LEN;
78 	ts[0] = htonl(cur_ts);
79 	ts[1] = htonl(cur_stream->rcvvar->ts_recent);
80 }
81 /*----------------------------------------------------------------------------*/
82 static inline void
83 GenerateTCPOptions(tcp_stream *cur_stream, uint32_t cur_ts,
84 		uint8_t flags, uint8_t *tcpopt, uint16_t optlen)
85 {
86 	int i = 0;
87 
88 	if (flags & TCP_FLAG_SYN) {
89 		uint16_t mss;
90 
91 		/* MSS option */
92 		mss = cur_stream->sndvar->mss;
93 		tcpopt[i++] = TCP_OPT_MSS;
94 		tcpopt[i++] = TCP_OPT_MSS_LEN;
95 		tcpopt[i++] = mss >> 8;
96 		tcpopt[i++] = mss % 256;
97 
98 		/* SACK permit */
99 #if TCP_OPT_SACK_ENABLED
100 #if !TCP_OPT_TIMESTAMP_ENABLED
101 		tcpopt[i++] = TCP_OPT_NOP;
102 		tcpopt[i++] = TCP_OPT_NOP;
103 #endif /* TCP_OPT_TIMESTAMP_ENABLED */
104 		tcpopt[i++] = TCP_OPT_SACK_PERMIT;
105 		tcpopt[i++] = TCP_OPT_SACK_PERMIT_LEN;
106 		TRACE_SACK("Local SACK permited.\n");
107 #endif /* TCP_OPT_SACK_ENABLED */
108 
109 		/* Timestamp */
110 #if TCP_OPT_TIMESTAMP_ENABLED
111 #if !TCP_OPT_SACK_ENABLED
112 		tcpopt[i++] = TCP_OPT_NOP;
113 		tcpopt[i++] = TCP_OPT_NOP;
114 #endif /* TCP_OPT_SACK_ENABLED */
115 		GenerateTCPTimestamp(cur_stream, tcpopt + i, cur_ts);
116 		i += TCP_OPT_TIMESTAMP_LEN;
117 #endif /* TCP_OPT_TIMESTAMP_ENABLED */
118 
119 		/* Window scale */
120 		tcpopt[i++] = TCP_OPT_NOP;
121 		tcpopt[i++] = TCP_OPT_WSCALE;
122 		tcpopt[i++] = TCP_OPT_WSCALE_LEN;
123 		tcpopt[i++] = cur_stream->sndvar->wscale_mine;
124 
125 	} else {
126 
127 #if TCP_OPT_TIMESTAMP_ENABLED
128 		tcpopt[i++] = TCP_OPT_NOP;
129 		tcpopt[i++] = TCP_OPT_NOP;
130 		GenerateTCPTimestamp(cur_stream, tcpopt + i, cur_ts);
131 		i += TCP_OPT_TIMESTAMP_LEN;
132 #endif
133 
134 #if TCP_OPT_SACK_ENABLED
135 		if (flags & TCP_OPT_SACK) {
136 			// TODO: implement SACK support
137 		}
138 #endif
139 	}
140 
141 	assert (i == optlen);
142 }
143 /*----------------------------------------------------------------------------*/
144 int
145 SendTCPPacketStandalone(struct mtcp_manager *mtcp,
146 		uint32_t saddr, uint16_t sport, uint32_t daddr, uint16_t dport,
147 		uint32_t seq, uint32_t ack_seq, uint16_t window, uint8_t flags,
148 		uint8_t *payload, uint16_t payloadlen,
149 		uint32_t cur_ts, uint32_t echo_ts, uint16_t ip_id)
150 {
151 	struct tcphdr *tcph;
152 	uint8_t *tcpopt;
153 	uint32_t *ts;
154 	uint16_t optlen;
155 	struct pkt_ctx pctx;
156 	int rc = -1;
157 
158 	memset(&pctx, 0, sizeof(pctx));
159 	optlen = CalculateOptionLength(flags);
160 	if (payloadlen > TCP_DEFAULT_MSS + optlen) {
161 		TRACE_ERROR("Payload size exceeds MSS.\n");
162 		assert(0);
163 		return ERROR;
164 	}
165 
166 	tcph = (struct tcphdr *)IPOutputStandalone(mtcp, 0,
167 			saddr, daddr, TCP_HEADER_LEN + optlen + payloadlen, &pctx, cur_ts);
168 	if (tcph == NULL) {
169 		return ERROR;
170 	}
171 	memset(tcph, 0, TCP_HEADER_LEN + optlen);
172 
173 	tcph->source = sport;
174 	tcph->dest = dport;
175 
176 	if (flags & TCP_FLAG_SYN)
177 		tcph->syn = TRUE;
178 	if (flags & TCP_FLAG_FIN)
179 		tcph->fin = TRUE;
180 	if (flags & TCP_FLAG_RST)
181 		tcph->rst = TRUE;
182 	if (flags & TCP_FLAG_PSH)
183 		tcph->psh = TRUE;
184 
185 	tcph->seq = htonl(seq);
186 	if (flags & TCP_FLAG_ACK) {
187 		tcph->ack = TRUE;
188 		tcph->ack_seq = htonl(ack_seq);
189 	}
190 
191 	tcph->window = htons(MIN(window, TCP_MAX_WINDOW));
192 
193 	tcpopt = (uint8_t *)tcph + TCP_HEADER_LEN;
194 	ts = (uint32_t *)(tcpopt + 4);
195 
196 	tcpopt[0] = TCP_OPT_NOP;
197 	tcpopt[1] = TCP_OPT_NOP;
198 	tcpopt[2] = TCP_OPT_TIMESTAMP;
199 	tcpopt[3] = TCP_OPT_TIMESTAMP_LEN;
200 	ts[0] = htonl(cur_ts);
201 	ts[1] = htonl(echo_ts);
202 
203 	tcph->doff = (TCP_HEADER_LEN + optlen) >> 2;
204 	// copy payload if exist
205 	if (payloadlen > 0) {
206 		memcpy((uint8_t *)tcph + TCP_HEADER_LEN + optlen, payload, payloadlen);
207 	}
208 
209 #if TCP_CALCULATE_CHECKSUM
210 	/* offload TCP checkum if possible */
211 	if (likely(mtcp->iom->dev_ioctl != NULL))
212 		rc = mtcp->iom->dev_ioctl(mtcp->ctx,
213 					  pctx.out_ifidx,
214 					  PKT_TX_TCP_CSUM,
215 					  pctx.p.iph);
216 	/* otherwise calculate TCP checksum in S/W */
217 	if (rc == -1)
218 		tcph->check = TCPCalcChecksum((uint16_t *)tcph,
219 					      TCP_HEADER_LEN +
220 					      optlen + payloadlen,
221 					      saddr, daddr);
222 #endif
223 
224 	if (tcph->syn || tcph->fin) {
225 		payloadlen++;
226 	}
227 
228 	struct mon_listener *walk;
229 	/* callback for monitor raw socket */
230 	TAILQ_FOREACH(walk, &mtcp->monitors, link)
231 		if (walk->socket->socktype == MOS_SOCK_MONITOR_RAW)
232 			HandleCallback(mtcp, MOS_NULL, walk->socket, MOS_SIDE_BOTH,
233 				       &pctx, MOS_ON_PKT_IN);
234 	return payloadlen;
235 }
236 /*----------------------------------------------------------------------------*/
237 int
238 SendTCPPacket(struct mtcp_manager *mtcp, tcp_stream *cur_stream,
239 		uint32_t cur_ts, uint8_t flags, uint8_t *payload, uint16_t payloadlen)
240 {
241 	struct tcphdr *tcph;
242 	uint16_t optlen;
243 	uint8_t wscale = 0;
244 	uint32_t window32 = 0;
245 	struct pkt_ctx pctx;
246 	int rc = -1;
247 
248 	memset(&pctx, 0, sizeof(pctx));
249 	optlen = CalculateOptionLength(flags);
250 	if (payloadlen > cur_stream->sndvar->mss + optlen) {
251 		TRACE_ERROR("Payload size exceeds MSS\n");
252 		return ERROR;
253 	}
254 
255 	tcph = (struct tcphdr *)IPOutput(mtcp, cur_stream,
256 			TCP_HEADER_LEN + optlen + payloadlen, &pctx, cur_ts);
257 	if (tcph == NULL) {
258 		return -2;
259 	}
260 	memset(tcph, 0, TCP_HEADER_LEN + optlen);
261 
262 	tcph->source = cur_stream->sport;
263 	tcph->dest = cur_stream->dport;
264 
265 	if (flags & TCP_FLAG_SYN) {
266 		tcph->syn = TRUE;
267 		if (cur_stream->snd_nxt != cur_stream->sndvar->iss) {
268 			TRACE_DBG("Stream %d: weird SYN sequence. "
269 					"snd_nxt: %u, iss: %u\n", cur_stream->id,
270 					cur_stream->snd_nxt, cur_stream->sndvar->iss);
271 		}
272 		TRACE_DBG("Stream %d: Sending SYN. seq: %u, ack_seq: %u\n",
273 			  cur_stream->id, cur_stream->snd_nxt, cur_stream->rcv_nxt);
274 	}
275 	if (flags & TCP_FLAG_RST) {
276 		TRACE_FIN("Stream %d: Sending RST.\n", cur_stream->id);
277 		tcph->rst = TRUE;
278 	}
279 	if (flags & TCP_FLAG_PSH)
280 		tcph->psh = TRUE;
281 
282 	if (flags & TCP_FLAG_WACK) {
283 		tcph->seq = htonl(cur_stream->snd_nxt - 1);
284 		TRACE_CLWND("%u Sending ACK to get new window advertisement. "
285 				"seq: %u, peer_wnd: %u, snd_nxt - snd_una: %u\n",
286 				cur_stream->id,
287 				cur_stream->snd_nxt - 1, cur_stream->sndvar->peer_wnd,
288 				cur_stream->snd_nxt - cur_stream->sndvar->snd_una);
289 	} else if (flags & TCP_FLAG_FIN) {
290 		tcph->fin = TRUE;
291 
292 		if (cur_stream->sndvar->fss == 0) {
293 			TRACE_ERROR("Stream %u: not fss set. closed: %u\n",
294 					cur_stream->id, cur_stream->closed);
295 		}
296 		tcph->seq = htonl(cur_stream->sndvar->fss);
297 		cur_stream->sndvar->is_fin_sent = TRUE;
298 		TRACE_FIN("Stream %d: Sending FIN. seq: %u, ack_seq: %u\n",
299 				cur_stream->id, cur_stream->snd_nxt, cur_stream->rcv_nxt);
300 	} else {
301 		tcph->seq = htonl(cur_stream->snd_nxt);
302 	}
303 
304 	if (flags & TCP_FLAG_ACK) {
305 		tcph->ack = TRUE;
306 		tcph->ack_seq = htonl(cur_stream->rcv_nxt);
307 		cur_stream->sndvar->ts_lastack_sent = cur_ts;
308 		cur_stream->last_active_ts = cur_ts;
309 		UpdateTimeoutList(mtcp, cur_stream);
310 	}
311 
312 	if (flags & TCP_FLAG_SYN) {
313 		wscale = 0;
314 	} else {
315 		wscale = cur_stream->sndvar->wscale_mine;
316 	}
317 
318 	window32 = cur_stream->rcvvar->rcv_wnd >> wscale;
319 	tcph->window = htons((uint16_t)MIN(window32, TCP_MAX_WINDOW));
320 	/* if the advertised window is 0, we need to advertise again later */
321 	if (window32 == 0) {
322 		cur_stream->need_wnd_adv = TRUE;
323 	}
324 
325 	GenerateTCPOptions(cur_stream, cur_ts, flags,
326 			(uint8_t *)tcph + TCP_HEADER_LEN, optlen);
327 
328 	tcph->doff = (TCP_HEADER_LEN + optlen) >> 2;
329 	// copy payload if exist
330 	if (payloadlen > 0) {
331 		memcpy((uint8_t *)tcph + TCP_HEADER_LEN + optlen, payload, payloadlen);
332 	}
333 
334 #if TCP_CALCULATE_CHECKSUM
335 	if (likely(mtcp->iom->dev_ioctl != NULL))
336 		rc = mtcp->iom->dev_ioctl(mtcp->ctx,
337 					  pctx.out_ifidx,
338 					  PKT_TX_TCP_CSUM,
339 					  pctx.p.iph);
340 	if (rc == -1)
341 		tcph->check = TCPCalcChecksum((uint16_t *)tcph,
342 					      TCP_HEADER_LEN +
343 					      optlen + payloadlen,
344 					      cur_stream->saddr,
345 					      cur_stream->daddr);
346 #endif
347 	cur_stream->snd_nxt += payloadlen;
348 
349 	if (tcph->syn || tcph->fin) {
350 		cur_stream->snd_nxt++;
351 		payloadlen++;
352 	}
353 
354 	if (payloadlen > 0) {
355 		if (cur_stream->state > TCP_ST_ESTABLISHED) {
356 			TRACE_FIN("Payload after ESTABLISHED: length: %d, snd_nxt: %u\n",
357 				  payloadlen, cur_stream->snd_nxt);
358 		}
359 
360 		/* update retransmission timer if have payload */
361 		cur_stream->sndvar->ts_rto = cur_ts + cur_stream->sndvar->rto;
362 		TRACE_RTO("Updating retransmission timer. "
363 				"cur_ts: %u, rto: %u, ts_rto: %u\n",
364 				cur_ts, cur_stream->sndvar->rto, cur_stream->sndvar->ts_rto);
365 		AddtoRTOList(mtcp, cur_stream);
366 	}
367 
368 	struct mon_listener *walk;
369 	/* callback for monitor raw socket */
370 	TAILQ_FOREACH(walk, &mtcp->monitors, link)
371 		if (walk->socket->socktype == MOS_SOCK_MONITOR_RAW)
372 			HandleCallback(mtcp, MOS_NULL, walk->socket, MOS_SIDE_BOTH,
373 				       &pctx, MOS_ON_PKT_IN);
374 
375 	if (mtcp->num_msp /* this means that stream monitor is on */) {
376 		FillPacketContextTCPInfo(&pctx, tcph);
377 
378 		/* New abstraction for monitor stream */
379 		struct tcp_stream *recvside_stream = cur_stream->pair_stream;
380 		struct tcp_stream *sendside_stream = cur_stream;
381 
382 		if (recvside_stream->rcvvar && recvside_stream->rcvvar->rcvbuf)
383 			pctx.p.offset = (uint64_t)seq2loff(recvside_stream->rcvvar->rcvbuf,
384 					pctx.p.seq, recvside_stream->rcvvar->irs + 1);
385 
386 		UpdateMonitor(mtcp, sendside_stream, recvside_stream, &pctx, false);
387 	}
388 
389 #ifdef PKTDUMP
390 	DumpPacket(mtcp,
391 			(char *)tcph - sizeof(struct iphdr) - sizeof(struct ethhdr),
392 			payloadlen + sizeof(struct iphdr) + sizeof(struct ethhdr),
393 			"OUT", -1);
394 #endif
395 
396 
397 	return payloadlen;
398 }
399 /*----------------------------------------------------------------------------*/
400 static int
401 FlushTCPSendingBuffer(mtcp_manager_t mtcp, tcp_stream *cur_stream, uint32_t cur_ts)
402 {
403 	struct tcp_send_vars *sndvar = cur_stream->sndvar;
404 	const uint32_t maxlen = sndvar->mss - CalculateOptionLength(TCP_FLAG_ACK);
405 	uint8_t *data;
406 	uint32_t buffered_len;
407 	uint32_t seq;
408 	uint16_t len;
409 	int16_t sndlen;
410 	uint32_t window;
411 	int packets = 0;
412 
413 	if (!sndvar->sndbuf) {
414 		TRACE_ERROR("Stream %d: No send buffer available.\n", cur_stream->id);
415 		assert(0);
416 		return 0;
417 	}
418 
419 	SBUF_LOCK(&sndvar->write_lock);
420 
421 	if (sndvar->sndbuf->len == 0) {
422 		packets = 0;
423 		goto out;
424 	}
425 
426 	window = MIN(sndvar->cwnd, sndvar->peer_wnd);
427 
428 	while (1) {
429 		seq = cur_stream->snd_nxt;
430 
431 		if (TCP_SEQ_LT(seq, sndvar->sndbuf->head_seq)) {
432 			TRACE_ERROR("Stream %d: Invalid sequence to send. "
433 					"state: %s, seq: %u, head_seq: %u.\n",
434 					cur_stream->id, TCPStateToString(cur_stream),
435 					seq, sndvar->sndbuf->head_seq);
436 			assert(0);
437 			break;
438 		}
439 		buffered_len = sndvar->sndbuf->head_seq + sndvar->sndbuf->len - seq;
440 		if (cur_stream->state > TCP_ST_ESTABLISHED) {
441 			TRACE_FIN("head_seq: %u, len: %u, seq: %u, "
442 					"buffered_len: %u\n", sndvar->sndbuf->head_seq,
443 					sndvar->sndbuf->len, seq, buffered_len);
444 		}
445 		if (buffered_len == 0)
446 			break;
447 
448 		data = sndvar->sndbuf->head +
449 				(seq - sndvar->sndbuf->head_seq);
450 
451 		if (buffered_len > maxlen) {
452 			len = maxlen;
453 		} else {
454 			len = buffered_len;
455 		}
456 
457 		if (len <= 0)
458 			break;
459 
460 		if (cur_stream->state > TCP_ST_ESTABLISHED) {
461 			TRACE_FIN("Flushing after ESTABLISHED: seq: %u, len: %u, "
462 					"buffered_len: %u\n", seq, len, buffered_len);
463 		}
464 
465 		if (seq - sndvar->snd_una + len > window) {
466 			/* Ask for new window advertisement to peer */
467 			if (seq - sndvar->snd_una + len > sndvar->peer_wnd) {
468 				TRACE_DBG("Full peer window. "
469 					  "peer_wnd: %u, (snd_nxt-snd_una): %u\n",
470 					  sndvar->peer_wnd, seq - sndvar->snd_una);
471 				if (TS_TO_MSEC(cur_ts - sndvar->ts_lastack_sent) > 500) {
472 					EnqueueACK(mtcp, cur_stream, cur_ts, ACK_OPT_WACK);
473 				}
474 			}
475 			packets = -3;
476 			goto out;
477 		}
478 
479 		sndlen = SendTCPPacket(mtcp, cur_stream, cur_ts,
480 				TCP_FLAG_ACK, data, len);
481 		if (sndlen < 0) {
482 			packets = sndlen;
483 			goto out;
484 		}
485 		packets++;
486 	}
487 
488  out:
489 	SBUF_UNLOCK(&sndvar->write_lock);
490 	return packets;
491 }
492 /*----------------------------------------------------------------------------*/
493 static inline int
494 SendControlPacket(mtcp_manager_t mtcp, tcp_stream *cur_stream, uint32_t cur_ts)
495 {
496 	struct tcp_send_vars *sndvar = cur_stream->sndvar;
497 	int ret = 0;
498     int flag = 0;
499 
500     switch (cur_stream->state) {
501        case TCP_ST_SYN_SENT: 		/* Send SYN here */
502           flag = TCP_FLAG_SYN;
503           break;
504        case TCP_ST_SYN_RCVD:        /* Send SYN/ACK here */
505           cur_stream->snd_nxt = sndvar->iss;
506           flag = TCP_FLAG_SYN | TCP_FLAG_ACK;
507           break;
508        case TCP_ST_ESTABLISHED:     /* Send ACK here */
509        case TCP_ST_CLOSE_WAIT:	    /* Send ACK for the FIN here */
510        case TCP_ST_FIN_WAIT_2:      /* Send ACK here */
511        case TCP_ST_TIME_WAIT:       /* Send ACK here */
512           flag = TCP_FLAG_ACK;
513           break;
514        case TCP_ST_LAST_ACK:
515        case TCP_ST_FIN_WAIT_1:
516           /* if it is on ack_list, send it after sending ack */
517           if (sndvar->on_send_list || sndvar->on_ack_list)
518              return (-1);
519           flag = TCP_FLAG_FIN | TCP_FLAG_ACK; /* Send FIN/ACK here */
520           break;
521        case TCP_ST_CLOSING:
522           if (sndvar->is_fin_sent) {
523              /* if the sequence is for FIN, send FIN */
524              flag = (cur_stream->snd_nxt == sndvar->fss) ?
525                 (TCP_FLAG_FIN | TCP_FLAG_ACK) : TCP_FLAG_ACK;
526           } else {
527              /* if FIN is not sent, send fin with ack */
528              flag = TCP_FLAG_FIN | TCP_FLAG_ACK;
529           }
530        case TCP_ST_CLOSED_RSVD: /* Send RST here */
531           TRACE_DBG("Stream %d: Try sending RST (TCP_ST_CLOSED_RSVD)\n",
532                     cur_stream->id);
533           /* first flush the data and ack */
534           if (sndvar->on_send_list || sndvar->on_ack_list)
535              return (-1);
536           ret = SendTCPPacket(mtcp, cur_stream, cur_ts, TCP_FLAG_RST, NULL, 0);
537           if (ret >= 0)
538              DestroyTCPStream(mtcp, cur_stream);
539           return (ret);
540        default:
541           TRACE_ERROR("Stream %d: shouldn't send a control packet\n",
542                       cur_stream->id);
543           assert(0); /* can't reach here! */
544           return (0);
545     }
546 
547     return SendTCPPacket(mtcp, cur_stream, cur_ts, flag, NULL, 0);
548 }
549 /*----------------------------------------------------------------------------*/
550 inline int
551 WriteTCPControlList(mtcp_manager_t mtcp,
552 		struct mtcp_sender *sender, uint32_t cur_ts, int thresh)
553 {
554 	tcp_stream *cur_stream;
555 	tcp_stream *next, *last;
556 	int cnt = 0;
557 	int ret;
558 
559 	thresh = MIN(thresh, sender->control_list_cnt);
560 
561 	/* Send TCP control messages */
562 	cnt = 0;
563 	cur_stream = TAILQ_FIRST(&sender->control_list);
564 	last = TAILQ_LAST(&sender->control_list, control_head);
565 	while (cur_stream) {
566 		if (++cnt > thresh)
567 			break;
568 
569 		TRACE_LOOP("Inside control loop. cnt: %u, stream: %d\n",
570 				cnt, cur_stream->id);
571 		next = TAILQ_NEXT(cur_stream, sndvar->control_link);
572 
573 		TAILQ_REMOVE(&sender->control_list, cur_stream, sndvar->control_link);
574 		sender->control_list_cnt--;
575 
576 		if (cur_stream->sndvar->on_control_list) {
577 			cur_stream->sndvar->on_control_list = FALSE;
578 			//TRACE_DBG("Stream %u: Sending control packet\n", cur_stream->id);
579 			ret = SendControlPacket(mtcp, cur_stream, cur_ts);
580 			if (ret < 0) {
581 				TAILQ_INSERT_HEAD(&sender->control_list,
582 						cur_stream, sndvar->control_link);
583 				cur_stream->sndvar->on_control_list = TRUE;
584 				sender->control_list_cnt++;
585 				/* since there is no available write buffer, break */
586 				break;
587 			}
588 		} else {
589 			TRACE_ERROR("Stream %d: not on control list.\n", cur_stream->id);
590 		}
591 
592 		if (cur_stream == last)
593 			break;
594 		cur_stream = next;
595 	}
596 
597 	return cnt;
598 }
599 /*----------------------------------------------------------------------------*/
600 inline int
601 WriteTCPDataList(mtcp_manager_t mtcp,
602 		struct mtcp_sender *sender, uint32_t cur_ts, int thresh)
603 {
604 	tcp_stream *cur_stream;
605 	tcp_stream *next, *last;
606 	int cnt = 0;
607 	int ret;
608 
609 	/* Send data */
610 	cnt = 0;
611 	cur_stream = TAILQ_FIRST(&sender->send_list);
612 	last = TAILQ_LAST(&sender->send_list, send_head);
613 	while (cur_stream) {
614 		if (++cnt > thresh)
615 			break;
616 
617 		TRACE_LOOP("Inside send loop. cnt: %u, stream: %d\n",
618 				cnt, cur_stream->id);
619 		next = TAILQ_NEXT(cur_stream, sndvar->send_link);
620 
621 		TAILQ_REMOVE(&sender->send_list, cur_stream, sndvar->send_link);
622 		if (cur_stream->sndvar->on_send_list) {
623 			ret = 0;
624 
625 			/* Send data here */
626 			/* Only can send data when ESTABLISHED or CLOSE_WAIT */
627 			if (cur_stream->state == TCP_ST_ESTABLISHED) {
628 				if (cur_stream->sndvar->on_control_list) {
629 					/* delay sending data after until on_control_list becomes off */
630 					//TRACE_DBG("Stream %u: delay sending data.\n", cur_stream->id);
631 					ret = -1;
632 				} else {
633 					ret = FlushTCPSendingBuffer(mtcp, cur_stream, cur_ts);
634 				}
635 			} else if (cur_stream->state == TCP_ST_CLOSE_WAIT ||
636 					cur_stream->state == TCP_ST_FIN_WAIT_1 ||
637 					cur_stream->state == TCP_ST_LAST_ACK) {
638 				ret = FlushTCPSendingBuffer(mtcp, cur_stream, cur_ts);
639 			} else {
640 				TRACE_DBG("Stream %d: on_send_list at state %s\n",
641 						cur_stream->id, TCPStateToString(cur_stream));
642 #if DUMP_STREAM
643 				DumpStream(mtcp, cur_stream);
644 #endif
645 			}
646 
647 			if (ret < 0) {
648 				TAILQ_INSERT_TAIL(&sender->send_list, cur_stream, sndvar->send_link);
649 				/* since there is no available write buffer, break */
650 				break;
651 
652 			} else {
653 				cur_stream->sndvar->on_send_list = FALSE;
654 				sender->send_list_cnt--;
655 				/* the ret value is the number of packets sent. */
656 				/* decrease ack_cnt for the piggybacked acks */
657 #if ACK_PIGGYBACK
658 				if (cur_stream->sndvar->ack_cnt > 0) {
659 					if (cur_stream->sndvar->ack_cnt > ret) {
660 						cur_stream->sndvar->ack_cnt -= ret;
661 					} else {
662 						cur_stream->sndvar->ack_cnt = 0;
663 					}
664 				}
665 #endif
666 #if 1
667 				if (cur_stream->control_list_waiting) {
668 					if (!cur_stream->sndvar->on_ack_list) {
669 						cur_stream->control_list_waiting = FALSE;
670 						AddtoControlList(mtcp, cur_stream, cur_ts);
671 					}
672 				}
673 #endif
674 			}
675 		} else {
676 			TRACE_ERROR("Stream %d: not on send list.\n", cur_stream->id);
677 #ifdef DUMP_STREAM
678 			DumpStream(mtcp, cur_stream);
679 #endif
680 		}
681 
682 		if (cur_stream == last)
683 			break;
684 		cur_stream = next;
685 	}
686 
687 	return cnt;
688 }
689 /*----------------------------------------------------------------------------*/
690 inline int
691 WriteTCPACKList(mtcp_manager_t mtcp,
692 		struct mtcp_sender *sender, uint32_t cur_ts, int thresh)
693 {
694 	tcp_stream *cur_stream;
695 	tcp_stream *next, *last;
696 	int to_ack;
697 	int cnt = 0;
698 	int ret;
699 
700 	/* Send aggregated acks */
701 	cnt = 0;
702 	cur_stream = TAILQ_FIRST(&sender->ack_list);
703 	last = TAILQ_LAST(&sender->ack_list, ack_head);
704 	while (cur_stream) {
705 		if (++cnt > thresh)
706 			break;
707 
708 		TRACE_LOOP("Inside ack loop. cnt: %u\n", cnt);
709 		next = TAILQ_NEXT(cur_stream, sndvar->ack_link);
710 
711 		if (cur_stream->sndvar->on_ack_list) {
712 			/* this list is only to ack the data packets */
713 			/* if the ack is not data ack, then it will not process here */
714 			to_ack = FALSE;
715 			if (cur_stream->state == TCP_ST_ESTABLISHED ||
716 					cur_stream->state == TCP_ST_CLOSE_WAIT ||
717 					cur_stream->state == TCP_ST_FIN_WAIT_1 ||
718 					cur_stream->state == TCP_ST_FIN_WAIT_2 ||
719 					cur_stream->state == TCP_ST_TIME_WAIT) {
720 				/* TIMEWAIT is possible since the ack is queued
721 				   at FIN_WAIT_2 */
722 				tcprb_t *rb;
723 				if ((rb = cur_stream->rcvvar->rcvbuf) &&
724 					TCP_SEQ_LEQ(cur_stream->rcv_nxt,
725 						(cur_stream->rcvvar->irs + 1) + rb->pile
726 						+ tcprb_cflen(rb))) {
727 					to_ack = TRUE;
728 				}
729 			} else {
730 				TRACE_DBG("Stream %u (%s): "
731 						"Try sending ack at not proper state. "
732 						"seq: %u, ack_seq: %u, on_control_list: %u\n",
733 						cur_stream->id, TCPStateToString(cur_stream),
734 						cur_stream->snd_nxt, cur_stream->rcv_nxt,
735 						cur_stream->sndvar->on_control_list);
736 #ifdef DUMP_STREAM
737 				DumpStream(mtcp, cur_stream);
738 #endif
739 			}
740 
741 			if (to_ack) {
742 				/* send the queued ack packets */
743 				while (cur_stream->sndvar->ack_cnt > 0) {
744 					ret = SendTCPPacket(mtcp, cur_stream,
745 							cur_ts, TCP_FLAG_ACK, NULL, 0);
746 					if (ret < 0) {
747 						/* since there is no available write buffer, break */
748 						break;
749 					}
750 					cur_stream->sndvar->ack_cnt--;
751 				}
752 
753 				/* if is_wack is set, send packet to get window advertisement */
754 				if (cur_stream->sndvar->is_wack) {
755 					cur_stream->sndvar->is_wack = FALSE;
756 					ret = SendTCPPacket(mtcp, cur_stream,
757 							cur_ts, TCP_FLAG_ACK | TCP_FLAG_WACK, NULL, 0);
758 					if (ret < 0) {
759 						/* since there is no available write buffer, break */
760 						cur_stream->sndvar->is_wack = TRUE;
761 					}
762 				}
763 
764 				if (!(cur_stream->sndvar->ack_cnt || cur_stream->sndvar->is_wack)) {
765 					cur_stream->sndvar->on_ack_list = FALSE;
766 					TAILQ_REMOVE(&sender->ack_list, cur_stream, sndvar->ack_link);
767 					sender->ack_list_cnt--;
768 				}
769 			} else {
770 				cur_stream->sndvar->on_ack_list = FALSE;
771 				cur_stream->sndvar->ack_cnt = 0;
772 				cur_stream->sndvar->is_wack = 0;
773 				TAILQ_REMOVE(&sender->ack_list, cur_stream, sndvar->ack_link);
774 				sender->ack_list_cnt--;
775 			}
776 
777 			if (cur_stream->control_list_waiting) {
778 				if (!cur_stream->sndvar->on_send_list) {
779 					cur_stream->control_list_waiting = FALSE;
780 					AddtoControlList(mtcp, cur_stream, cur_ts);
781 				}
782 			}
783 		} else {
784 			TRACE_ERROR("Stream %d: not on ack list.\n", cur_stream->id);
785 			TAILQ_REMOVE(&sender->ack_list, cur_stream, sndvar->ack_link);
786 			sender->ack_list_cnt--;
787 #ifdef DUMP_STREAM
788 			thread_printf(mtcp, mtcp->log_fp,
789 					"Stream %u: not on ack list.\n", cur_stream->id);
790 			DumpStream(mtcp, cur_stream);
791 #endif
792 		}
793 
794 		if (cur_stream == last)
795 			break;
796 		cur_stream = next;
797 	}
798 
799 	return cnt;
800 }
801 /*----------------------------------------------------------------------------*/
802 inline struct mtcp_sender *
803 GetSender(mtcp_manager_t mtcp, tcp_stream *cur_stream)
804 {
805 	if (cur_stream->sndvar->nif_out < 0) {
806 		return mtcp->g_sender;
807 
808 	} else if (cur_stream->sndvar->nif_out >= g_config.mos->netdev_table->num) {
809 		TRACE_ERROR("(NEVER HAPPEN) Failed to find appropriate sender.\n");
810 		return NULL;
811 
812 	} else {
813 		return mtcp->n_sender[cur_stream->sndvar->nif_out];
814 	}
815 }
816 /*----------------------------------------------------------------------------*/
817 inline void
818 AddtoControlList(mtcp_manager_t mtcp, tcp_stream *cur_stream, uint32_t cur_ts)
819 {
820 #if TRY_SEND_BEFORE_QUEUE
821 	int ret;
822 	struct mtcp_sender *sender = GetSender(mtcp, cur_stream);
823 	assert(sender != NULL);
824 
825 	ret = SendControlPacket(mtcp, cur_stream, cur_ts);
826 	if (ret < 0) {
827 #endif
828 		if (!cur_stream->sndvar->on_control_list) {
829 			struct mtcp_sender *sender = GetSender(mtcp, cur_stream);
830 			assert(sender != NULL);
831 
832 			cur_stream->sndvar->on_control_list = TRUE;
833 			TAILQ_INSERT_TAIL(&sender->control_list, cur_stream, sndvar->control_link);
834 			sender->control_list_cnt++;
835 			//TRACE_DBG("Stream %u: added to control list (cnt: %d)\n",
836 			//		cur_stream->id, sender->control_list_cnt);
837 		}
838 #if TRY_SEND_BEFORE_QUEUE
839 	} else {
840 		if (cur_stream->sndvar->on_control_list) {
841 			cur_stream->sndvar->on_control_list = FALSE;
842 			TAILQ_REMOVE(&sender->control_list, cur_stream, sndvar->control_link);
843 			sender->control_list_cnt--;
844 		}
845 	}
846 #endif
847 }
848 /*----------------------------------------------------------------------------*/
849 inline void
850 AddtoSendList(mtcp_manager_t mtcp, tcp_stream *cur_stream)
851 {
852 	struct mtcp_sender *sender = GetSender(mtcp, cur_stream);
853 	assert(sender != NULL);
854 
855 	if(!cur_stream->sndvar->sndbuf) {
856 		TRACE_ERROR("[%d] Stream %d: No send buffer available.\n",
857 				mtcp->ctx->cpu,
858 				cur_stream->id);
859 		assert(0);
860 		return;
861 	}
862 
863 	if (!cur_stream->sndvar->on_send_list) {
864 		cur_stream->sndvar->on_send_list = TRUE;
865 		TAILQ_INSERT_TAIL(&sender->send_list, cur_stream, sndvar->send_link);
866 		sender->send_list_cnt++;
867 	}
868 }
869 /*----------------------------------------------------------------------------*/
870 inline void
871 AddtoACKList(mtcp_manager_t mtcp, tcp_stream *cur_stream)
872 {
873 	struct mtcp_sender *sender = GetSender(mtcp, cur_stream);
874 	assert(sender != NULL);
875 
876 	if (!cur_stream->sndvar->on_ack_list) {
877 		cur_stream->sndvar->on_ack_list = TRUE;
878 		TAILQ_INSERT_TAIL(&sender->ack_list, cur_stream, sndvar->ack_link);
879 		sender->ack_list_cnt++;
880 	}
881 }
882 /*----------------------------------------------------------------------------*/
883 inline void
884 RemoveFromControlList(mtcp_manager_t mtcp, tcp_stream *cur_stream)
885 {
886 	struct mtcp_sender *sender = GetSender(mtcp, cur_stream);
887 	assert(sender != NULL);
888 
889 	if (cur_stream->sndvar->on_control_list) {
890 		cur_stream->sndvar->on_control_list = FALSE;
891 		TAILQ_REMOVE(&sender->control_list, cur_stream, sndvar->control_link);
892 		sender->control_list_cnt--;
893 		//TRACE_DBG("Stream %u: Removed from control list (cnt: %d)\n",
894 		//		cur_stream->id, sender->control_list_cnt);
895 	}
896 }
897 /*----------------------------------------------------------------------------*/
898 inline void
899 RemoveFromSendList(mtcp_manager_t mtcp, tcp_stream *cur_stream)
900 {
901 	struct mtcp_sender *sender = GetSender(mtcp, cur_stream);
902 	assert(sender != NULL);
903 
904 	if (cur_stream->sndvar->on_send_list) {
905 		cur_stream->sndvar->on_send_list = FALSE;
906 		TAILQ_REMOVE(&sender->send_list, cur_stream, sndvar->send_link);
907 		sender->send_list_cnt--;
908 	}
909 }
910 /*----------------------------------------------------------------------------*/
911 inline void
912 RemoveFromACKList(mtcp_manager_t mtcp, tcp_stream *cur_stream)
913 {
914 	struct mtcp_sender *sender = GetSender(mtcp, cur_stream);
915 	assert(sender != NULL);
916 
917 	if (cur_stream->sndvar->on_ack_list) {
918 		cur_stream->sndvar->on_ack_list = FALSE;
919 		TAILQ_REMOVE(&sender->ack_list, cur_stream, sndvar->ack_link);
920 		sender->ack_list_cnt--;
921 	}
922 }
923 /*----------------------------------------------------------------------------*/
924 inline void
925 EnqueueACK(mtcp_manager_t mtcp,
926 		tcp_stream *cur_stream, uint32_t cur_ts, uint8_t opt)
927 {
928 	if (!(cur_stream->state == TCP_ST_ESTABLISHED ||
929 			cur_stream->state == TCP_ST_CLOSE_WAIT ||
930 			cur_stream->state == TCP_ST_FIN_WAIT_1 ||
931 			cur_stream->state == TCP_ST_FIN_WAIT_2)) {
932 		TRACE_DBG("Stream %u: Enqueueing ack at state %s\n",
933 				cur_stream->id, TCPStateToString(cur_stream));
934 	}
935 
936 	if (opt == ACK_OPT_NOW) {
937 		if (cur_stream->sndvar->ack_cnt < cur_stream->sndvar->ack_cnt + 1) {
938 			cur_stream->sndvar->ack_cnt++;
939 		}
940 	} else if (opt == ACK_OPT_AGGREGATE) {
941 		if (cur_stream->sndvar->ack_cnt == 0) {
942 			cur_stream->sndvar->ack_cnt = 1;
943 		}
944 	} else if (opt == ACK_OPT_WACK) {
945 		cur_stream->sndvar->is_wack = TRUE;
946 	}
947 	AddtoACKList(mtcp, cur_stream);
948 }
949 /*----------------------------------------------------------------------------*/
950 inline void
951 DumpControlList(mtcp_manager_t mtcp, struct mtcp_sender *sender)
952 {
953 	tcp_stream *stream;
954 
955 	TRACE_DBG("Dumping control list (count: %d):\n", sender->control_list_cnt);
956 	TAILQ_FOREACH(stream, &sender->control_list, sndvar->control_link) {
957 		TRACE_DBG("Stream id: %u in control list\n", stream->id);
958 	}
959 }
960 /*----------------------------------------------------------------------------*/
961 static inline void
962 UpdatePassiveSendTCPContext_SynSent(struct tcp_stream *cur_stream,
963 				    struct pkt_ctx *pctx)
964 {
965 	assert(cur_stream);
966 	assert(pctx);
967 
968 	/* add event */
969 	if (cur_stream->state < TCP_ST_SYN_SENT) {
970 		cur_stream->cb_events |= MOS_ON_TCP_STATE_CHANGE;
971 		cur_stream->cb_events |= MOS_ON_CONN_START;
972 	}
973 	/* initialize TCP send variables of send-side stream */
974 	cur_stream->sndvar->cwnd = 1;
975 	cur_stream->sndvar->ssthresh = cur_stream->sndvar->mss * 10;
976 	cur_stream->sndvar->ip_id = htons(pctx->p.iph->id);
977 	cur_stream->sndvar->iss = pctx->p.seq;
978 	cur_stream->snd_nxt = pctx->p.seq + 1;
979 	cur_stream->state = TCP_ST_SYN_SENT;
980 	cur_stream->last_active_ts = pctx->p.cur_ts;
981 
982 	/* receive-side conn start event can also be tagged here */
983 	/* blocked since tcp_in.c takes care of this.. */
984 	/* cur_stream->pair_stream->cb_events |= MOS_ON_CONN_START; */
985 }
986 /*----------------------------------------------------------------------------*/
987 /**
988  * Called (when monitoring mode is enabled).. for every incoming packet from the
989  * NIC.
990  */
991 void
992 UpdatePassiveSendTCPContext(mtcp_manager_t mtcp, struct tcp_stream *cur_stream,
993 			    struct pkt_ctx *pctx)
994 {
995 	struct tcphdr *tcph;
996 
997 	assert(cur_stream);
998 	tcph = pctx->p.tcph;
999 
1000 	/* if it is a new TCP stream from client */
1001 	if (tcph->syn && !tcph->ack && cur_stream->state <= TCP_ST_SYN_SENT) {
1002 		TRACE_STATE("Stream %d: %s\n",
1003 			    cur_stream->id, TCPStateToString(cur_stream));
1004 		UpdatePassiveSendTCPContext_SynSent(cur_stream, pctx);
1005 		AddtoTimeoutList(mtcp, cur_stream);
1006 		return;
1007 	}
1008 
1009 	if (tcph->ack) {
1010 		cur_stream->sndvar->ts_lastack_sent = pctx->p.cur_ts;
1011 		cur_stream->last_active_ts = pctx->p.cur_ts;
1012 	}
1013 
1014 	cur_stream->snd_nxt = pctx->p.seq + pctx->p.payloadlen;
1015 
1016 	/* test for reset packet */
1017 	if (tcph->rst) {
1018 		cur_stream->have_reset = TRUE;
1019 		/* test for reset packet */
1020 		cur_stream->state = TCP_ST_CLOSED_RSVD;
1021 		cur_stream->cb_events |= MOS_ON_TCP_STATE_CHANGE;
1022 		TRACE_STATE("Stream %d: %s\n",
1023 				cur_stream->id,
1024 				TCPStateToString(cur_stream));
1025 		return;
1026 	}
1027 
1028 	/*
1029 	 * for all others, state transitioning is based on
1030 	 * current tcp_stream state
1031 	 */
1032 	switch (cur_stream->state) {
1033 	case TCP_ST_SYN_SENT:
1034 		/* control should not come here */
1035 		/* UpdatePassiveReceiveTCPContext() should take care of this */
1036 #ifdef BE_RESILIENT_TO_PACKET_DROP
1037 		if (tcph->ack && TCP_SEQ_GT(pctx->p.seq, cur_stream->sndvar->iss)) {
1038 			cur_stream->state = TCP_ST_ESTABLISHED;
1039 			cur_stream->cb_events |= MOS_ON_TCP_STATE_CHANGE;
1040 			cur_stream->snd_nxt = pctx->p.seq;
1041 			cur_stream->rcv_nxt = pctx->p.ack_seq;
1042 			goto __Handle_TCP_ST_ESTABLISHED;
1043 		}
1044 #endif
1045 		break;
1046 	case TCP_ST_SYN_RCVD:
1047 		if (!tcph->ack)
1048 			break;
1049 
1050 		if (tcph->syn) {
1051 			cur_stream->sndvar->iss = pctx->p.seq;
1052 			cur_stream->snd_nxt = cur_stream->sndvar->iss + 1;
1053 			TRACE_DBG("Stream %d (TCP_ST_SYN_RCVD): "
1054 				  "setting seq: %u = iss\n",
1055 				  cur_stream->id, pctx->p.seq);
1056 		}
1057 #ifdef BE_RESILIENT_TO_PACKET_DROP
1058 		else {
1059 			cur_stream->state = TCP_ST_ESTABLISHED;
1060 			cur_stream->cb_events |= MOS_ON_TCP_STATE_CHANGE;
1061 			cur_stream->snd_nxt = pctx->p.seq;
1062 			cur_stream->rcv_nxt = pctx->p.ack_seq;
1063 			goto __Handle_TCP_ST_ESTABLISHED;
1064 		}
1065 #endif
1066 		TRACE_STATE("Stream %d: %s\n",
1067 			    cur_stream->id,
1068 			    TCPStateToString(cur_stream));
1069 		break;
1070 	case TCP_ST_ESTABLISHED:
1071 #ifdef BE_RESILIENT_TO_PACKET_DROP
1072 __Handle_TCP_ST_ESTABLISHED:
1073 #endif
1074 		/* if application decides to close, fin pkt is sent */
1075 #ifdef BE_RESILIENT_TO_PACKET_DROP
1076 		if (tcph->ack && TCP_SEQ_GT(ntohl(tcph->ack_seq), cur_stream->rcv_nxt))
1077 		{
1078 			RAISE_DEBUG_EVENT(mtcp, cur_stream,
1079 					"Move rcv_nxt from %u to %u.\n",
1080 					cur_stream->rcv_nxt, ntohl(tcph->ack_seq));
1081 			cur_stream->rcv_nxt = ntohl(tcph->ack_seq);
1082 		}
1083 #endif
1084 		if (tcph->fin) {
1085 			cur_stream->state = TCP_ST_FIN_WAIT_1;
1086 			cur_stream->cb_events |= MOS_ON_TCP_STATE_CHANGE;
1087 			cur_stream->sndvar->fss = pctx->p.seq + pctx->p.payloadlen;
1088 			cur_stream->sndvar->is_fin_sent = TRUE;
1089 			cur_stream->snd_nxt++;
1090 			TRACE_STATE("Stream %d: %s\n",
1091 				    cur_stream->id,
1092 				    TCPStateToString(cur_stream));
1093 		} else {
1094 			/* creating tcp send buffer still pending.. */
1095 			/* do we need peek for send buffer? */
1096 		}
1097 		break;
1098 	case TCP_ST_CLOSE_WAIT:
1099 		/* if application decides to close, fin pkt is sent */
1100 #ifdef BE_RESILIENT_TO_PACKET_DROP
1101 		if (tcph->ack && TCP_SEQ_GT(ntohl(tcph->ack_seq), cur_stream->rcv_nxt))
1102 		{
1103 			RAISE_DEBUG_EVENT(mtcp, cur_stream,
1104 					"Move rcv_nxt from %u to %u.\n",
1105 					cur_stream->rcv_nxt, ntohl(tcph->ack_seq));
1106 			cur_stream->rcv_nxt = ntohl(tcph->ack_seq);
1107 		}
1108 #endif
1109 		if (tcph->fin) {
1110 			cur_stream->sndvar->fss = pctx->p.seq + pctx->p.payloadlen;
1111 			cur_stream->sndvar->is_fin_sent = TRUE;
1112 			cur_stream->snd_nxt++;
1113 			cur_stream->state = TCP_ST_LAST_ACK;
1114 			cur_stream->cb_events |= MOS_ON_TCP_STATE_CHANGE;
1115 			TRACE_STATE("Stream %d: %s\n",
1116 				    cur_stream->id,
1117 				    TCPStateToString(cur_stream));
1118 		} else if (tcph->ack) {
1119 			TRACE_STATE("Stream %d: %s\n",
1120 				    cur_stream->id,
1121 				    TCPStateToString(cur_stream));
1122 		}
1123 		break;
1124 	case TCP_ST_LAST_ACK:
1125 		/* control should not come here */
1126 		/* UpdatePassiveReceiveTCPContext() should take care of this */
1127 		break;
1128 	case TCP_ST_FIN_WAIT_1:
1129 		/* control should not come here */
1130 		/* UpdatePassiveReceiveTCPContext() should take care of this */
1131 		break;
1132 	case TCP_ST_FIN_WAIT_2:
1133 		/* control should not come here */
1134 		/* UpdatePassiveReceiveTCPContext() should take care of this */
1135 		break;
1136 	case TCP_ST_CLOSING:
1137 		/* control should not come here */
1138 		/* UpdatePassiveReceiveTCPContext() should take care of this */
1139 		break;
1140 	case TCP_ST_TIME_WAIT:
1141 		/* control may come here but... */
1142 		/* UpdatePassiveReceiveTCPContext() should take care of this */
1143 		if (tcph->ack) {
1144 			TRACE_STATE("Stream %d: %s\n",
1145 				    cur_stream->id,
1146 				    TCPStateToString(cur_stream));
1147 		}
1148 		break;
1149 	case TCP_ST_CLOSED:
1150 	case TCP_ST_CLOSED_RSVD:
1151 		/* Waiting to be destroyed */
1152 		break;
1153 	default:
1154 		TRACE_DBG("This should not happen.. Error state: %s reached!\n"
1155 			  "tcph->syn: %d, tcph->ack: %d\n",
1156 			  TCPStateToString(cur_stream), pctx->p.tcph->syn,
1157 			  pctx->p.tcph->ack);
1158 		assert(0);
1159 		/* This will be enabled once passiverecvcontext is completed */
1160 		/*exit(EXIT_FAILURE);*/
1161 	}
1162 
1163 	UNUSED(mtcp);
1164 	return;
1165 }
1166 /*----------------------------------------------------------------------------*/
1167 void
1168 PostSendTCPAction(mtcp_manager_t mtcp, struct pkt_ctx *pctx,
1169 		  struct tcp_stream *recvside_stream,
1170 		  struct tcp_stream *sendside_stream)
1171 {
1172 	uint32_t snd_seq_drift, rcv_seq_drift;
1173 
1174 	snd_seq_drift = FetchSeqDrift(sendside_stream, pctx->p.seq);
1175 	rcv_seq_drift = FetchSeqDrift(recvside_stream, pctx->p.ack_seq);
1176 
1177 	if (snd_seq_drift != 0 || rcv_seq_drift != 0) {
1178 		pctx->p.tcph->seq = htonl(pctx->p.seq +
1179 					  snd_seq_drift);
1180 		pctx->p.tcph->ack_seq = htonl(pctx->p.ack_seq -
1181 					      rcv_seq_drift);
1182 		pctx->p.seq += snd_seq_drift;
1183 		pctx->p.ack_seq -= rcv_seq_drift;
1184 
1185 		/* Recompute checksums */
1186 		pctx->p.iph->check = 0;
1187 		pctx->p.iph->check = ip_fast_csum(pctx->p.iph, pctx->p.iph->ihl);
1188 
1189 		pctx->p.tcph->check = 0;
1190 		pctx->p.tcph->check = TCPCalcChecksum((uint16_t *)pctx->p.tcph,
1191 			ntohs(pctx->p.iph->tot_len) - (pctx->p.iph->ihl<<2),
1192 			pctx->p.iph->saddr, pctx->p.iph->daddr);
1193 	}
1194 #if 0
1195 	/* This block of code will go away in future revisions */
1196 	/* update sequence no. if seq_drift > 0 */
1197 	if (sendside_stream->sndvar->seq_drift != 0 ||
1198 	    recvside_stream->sndvar->seq_drift != 0) {
1199 
1200 		pctx->p.tcph->seq = htonl(pctx->p.seq +
1201 					  sendside_stream->sndvar->seq_drift);
1202 		pctx->p.tcph->ack_seq = htonl(pctx->p.ack_seq -
1203 					      recvside_stream->sndvar->seq_drift);
1204 		pctx->p.seq += sendside_stream->sndvar->seq_drift;
1205 		pctx->p.ack_seq -= recvside_stream->sndvar->seq_drift;
1206 
1207 		/* Recompute checksums */
1208 		pctx->p.iph->check = 0;
1209 		pctx->p.iph->check = ip_fast_csum(pctx->p.iph, pctx->p.iph->ihl);
1210 
1211 		pctx->p.tcph->check = 0;
1212 		pctx->p.tcph->check = TCPCalcChecksum((uint16_t *)pctx->p.tcph,
1213 			ntohs(pctx->p.iph->tot_len) - (pctx->p.iph->ihl<<2),
1214 			pctx->p.iph->saddr, pctx->p.iph->daddr);
1215 	}
1216 #endif
1217 }
1218 /*----------------------------------------------------------------------------*/
1219