* highest SACK block). Also calculate the lowest snd_nxt among the remaining
* retransmitted skbs to avoid some costly processing per ACKs.
*/
-static int tcp_mark_lost_retrans(struct sock *sk)
+static void tcp_mark_lost_retrans(struct sock *sk)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *skb;
- int flag = 0;
int cnt = 0;
u32 new_low_seq = tp->snd_nxt;
u32 received_upto = TCP_SKB_CB(tp->highest_sack)->end_seq;
if (!tcp_is_fack(tp) || !tp->retrans_out ||
!after(received_upto, tp->lost_retrans_low) ||
icsk->icsk_ca_state != TCP_CA_Recovery)
- return flag;
+ return;
tcp_for_write_queue(skb, sk) {
u32 ack_seq = TCP_SKB_CB(skb)->ack_seq;
if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
tp->lost_out += tcp_skb_pcount(skb);
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
- flag |= FLAG_DATA_SACKED;
- NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
}
+ NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
} else {
if (before(ack_seq, new_low_seq))
new_low_seq = ack_seq;
if (tp->retrans_out)
tp->lost_retrans_low = new_low_seq;
-
- return flag;
}
static int tcp_check_dsack(struct tcp_sock *tp, struct sk_buff *ack_skb,
return in_sack;
}
+static int tcp_sacktag_one(struct sk_buff *skb, struct tcp_sock *tp,
+ int *reord, int dup_sack, int fack_count)
+{
+ u8 sacked = TCP_SKB_CB(skb)->sacked;
+ int flag = 0;
+
+ /* Account D-SACK for retransmitted packet. */
+ if (dup_sack && (sacked & TCPCB_RETRANS)) {
+ if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
+ tp->undo_retrans--;
+ if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una) &&
+ (sacked & TCPCB_SACKED_ACKED))
+ *reord = min(fack_count, *reord);
+ }
+
+ /* Nothing to do; acked frame is about to be dropped (was ACKed). */
+ if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
+ return flag;
+
+ if (!(sacked & TCPCB_SACKED_ACKED)) {
+ if (sacked & TCPCB_SACKED_RETRANS) {
+ /* If the segment is not tagged as lost,
+ * we do not clear RETRANS, believing
+ * that retransmission is still in flight.
+ */
+ if (sacked & TCPCB_LOST) {
+ TCP_SKB_CB(skb)->sacked &=
+ ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
+ tp->lost_out -= tcp_skb_pcount(skb);
+ tp->retrans_out -= tcp_skb_pcount(skb);
+
+ /* clear lost hint */
+ tp->retransmit_skb_hint = NULL;
+ }
+ } else {
+ if (!(sacked & TCPCB_RETRANS)) {
+ /* New sack for not retransmitted frame,
+ * which was in hole. It is reordering.
+ */
+ if (before(TCP_SKB_CB(skb)->seq,
+ tcp_highest_sack_seq(tp)))
+ *reord = min(fack_count, *reord);
+
+ /* SACK enhanced F-RTO (RFC4138; Appendix B) */
+ if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
+ flag |= FLAG_ONLY_ORIG_SACKED;
+ }
+
+ if (sacked & TCPCB_LOST) {
+ TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
+ tp->lost_out -= tcp_skb_pcount(skb);
+
+ /* clear lost hint */
+ tp->retransmit_skb_hint = NULL;
+ }
+ }
+
+ TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
+ flag |= FLAG_DATA_SACKED;
+ tp->sacked_out += tcp_skb_pcount(skb);
+
+ fack_count += tcp_skb_pcount(skb);
+
+ /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
+ if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
+ before(TCP_SKB_CB(skb)->seq,
+ TCP_SKB_CB(tp->lost_skb_hint)->seq))
+ tp->lost_cnt_hint += tcp_skb_pcount(skb);
+
+ if (fack_count > tp->fackets_out)
+ tp->fackets_out = fack_count;
+
+ if (after(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
+ tp->highest_sack = skb;
+
+ } else {
+ if (dup_sack && (sacked & TCPCB_RETRANS))
+ *reord = min(fack_count, *reord);
+ }
+
+ /* D-SACK. We can detect redundant retransmission in S|R and plain R
+ * frames and clear it. undo_retrans is decreased above, L|R frames
+ * are accounted above as well.
+ */
+ if (dup_sack && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) {
+ TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
+ tp->retrans_out -= tcp_skb_pcount(skb);
+ tp->retransmit_skb_hint = NULL;
+ }
+
+ return flag;
+}
+
+static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
+ struct tcp_sack_block *next_dup,
+ u32 start_seq, u32 end_seq,
+ int dup_sack_in, int *fack_count,
+ int *reord, int *flag)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ tcp_for_write_queue_from(skb, sk) {
+ int in_sack = 0;
+ int dup_sack = dup_sack_in;
+
+ if (skb == tcp_send_head(sk))
+ break;
+
+ /* queue is in-order => we can short-circuit the walk early */
+ if (!before(TCP_SKB_CB(skb)->seq, end_seq))
+ break;
+
+ if ((next_dup != NULL) &&
+ before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) {
+ in_sack = tcp_match_skb_to_sack(sk, skb,
+ next_dup->start_seq,
+ next_dup->end_seq);
+ if (in_sack > 0)
+ dup_sack = 1;
+ }
+
+ if (in_sack <= 0)
+ in_sack = tcp_match_skb_to_sack(sk, skb, start_seq, end_seq);
+ if (unlikely(in_sack < 0))
+ break;
+
+ if (in_sack)
+ *flag |= tcp_sacktag_one(skb, tp, reord, dup_sack, *fack_count);
+
+ *fack_count += tcp_skb_pcount(skb);
+ }
+ return skb;
+}
+
+/* Avoid all extra work that is being done by sacktag while walking in
+ * a normal way
+ */
+static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
+ u32 skip_to_seq)
+{
+ tcp_for_write_queue_from(skb, sk) {
+ if (skb == tcp_send_head(sk))
+ break;
+
+ if (!before(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
+ break;
+ }
+ return skb;
+}
+
+static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
+ struct sock *sk,
+ struct tcp_sack_block *next_dup,
+ u32 skip_to_seq,
+ int *fack_count, int *reord,
+ int *flag)
+{
+ if (next_dup == NULL)
+ return skb;
+
+ if (before(next_dup->start_seq, skip_to_seq)) {
+ skb = tcp_sacktag_skip(skb, sk, next_dup->start_seq);
+ tcp_sacktag_walk(skb, sk, NULL,
+ next_dup->start_seq, next_dup->end_seq,
+ 1, fack_count, reord, flag);
+ }
+
+ return skb;
+}
+
+static int tcp_sack_cache_ok(struct tcp_sock *tp, struct tcp_sack_block *cache)
+{
+ return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
+}
+
static int
tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
{
struct tcp_sock *tp = tcp_sk(sk);
unsigned char *ptr = (skb_transport_header(ack_skb) +
TCP_SKB_CB(ack_skb)->sacked);
- struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2);
- struct sk_buff *cached_skb;
+ struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
+ struct tcp_sack_block sp[4];
+ struct tcp_sack_block *cache;
+ struct sk_buff *skb;
int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
+ int used_sacks;
int reord = tp->packets_out;
int flag = 0;
int found_dup_sack = 0;
- int cached_fack_count;
- int i;
+ int fack_count;
+ int i, j;
int first_sack_index;
- int force_one_sack;
if (!tp->sacked_out) {
if (WARN_ON(tp->fackets_out))
tp->highest_sack = tcp_write_queue_head(sk);
}
- found_dup_sack = tcp_check_dsack(tp, ack_skb, sp,
+ found_dup_sack = tcp_check_dsack(tp, ack_skb, sp_wire,
num_sacks, prior_snd_una);
if (found_dup_sack)
flag |= FLAG_DSACKING_ACK;
if (!tp->packets_out)
goto out;
- /* SACK fastpath:
- * if the only SACK change is the increase of the end_seq of
- * the first block then only apply that SACK block
- * and use retrans queue hinting otherwise slowpath */
- force_one_sack = 1;
- for (i = 0; i < num_sacks; i++) {
- __be32 start_seq = sp[i].start_seq;
- __be32 end_seq = sp[i].end_seq;
-
- if (i == 0) {
- if (tp->recv_sack_cache[i].start_seq != start_seq)
- force_one_sack = 0;
- } else {
- if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
- (tp->recv_sack_cache[i].end_seq != end_seq))
- force_one_sack = 0;
- }
- tp->recv_sack_cache[i].start_seq = start_seq;
- tp->recv_sack_cache[i].end_seq = end_seq;
- }
- /* Clear the rest of the cache sack blocks so they won't match mistakenly. */
- for (; i < ARRAY_SIZE(tp->recv_sack_cache); i++) {
- tp->recv_sack_cache[i].start_seq = 0;
- tp->recv_sack_cache[i].end_seq = 0;
- }
-
+ used_sacks = 0;
first_sack_index = 0;
- if (force_one_sack)
- num_sacks = 1;
- else {
- int j;
- tp->fastpath_skb_hint = NULL;
-
- /* order SACK blocks to allow in order walk of the retrans queue */
- for (i = num_sacks-1; i > 0; i--) {
- for (j = 0; j < i; j++){
- if (after(ntohl(sp[j].start_seq),
- ntohl(sp[j+1].start_seq))){
- struct tcp_sack_block_wire tmp;
-
- tmp = sp[j];
- sp[j] = sp[j+1];
- sp[j+1] = tmp;
-
- /* Track where the first SACK block goes to */
- if (j == first_sack_index)
- first_sack_index = j+1;
- }
-
- }
- }
- }
-
- /* Use SACK fastpath hint if valid */
- cached_skb = tp->fastpath_skb_hint;
- cached_fack_count = tp->fastpath_cnt_hint;
- if (!cached_skb) {
- cached_skb = tcp_write_queue_head(sk);
- cached_fack_count = 0;
- }
-
for (i = 0; i < num_sacks; i++) {
- struct sk_buff *skb;
- __u32 start_seq = ntohl(sp->start_seq);
- __u32 end_seq = ntohl(sp->end_seq);
- int fack_count;
- int dup_sack = (found_dup_sack && (i == first_sack_index));
- int next_dup = (found_dup_sack && (i+1 == first_sack_index));
+ int dup_sack = !i && found_dup_sack;
- sp++;
+ sp[used_sacks].start_seq = ntohl(get_unaligned(&sp_wire[i].start_seq));
+ sp[used_sacks].end_seq = ntohl(get_unaligned(&sp_wire[i].end_seq));
- if (!tcp_is_sackblock_valid(tp, dup_sack, start_seq, end_seq)) {
+ if (!tcp_is_sackblock_valid(tp, dup_sack,
+ sp[used_sacks].start_seq,
+ sp[used_sacks].end_seq)) {
if (dup_sack) {
if (!tp->undo_marker)
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDNOUNDO);
} else {
/* Don't count olds caused by ACK reordering */
if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
- !after(end_seq, tp->snd_una))
+ !after(sp[used_sacks].end_seq, tp->snd_una))
continue;
NET_INC_STATS_BH(LINUX_MIB_TCPSACKDISCARD);
}
+ if (i == 0)
+ first_sack_index = -1;
continue;
}
- skb = cached_skb;
- fack_count = cached_fack_count;
+ /* Ignore very old stuff early */
+ if (!after(sp[used_sacks].end_seq, prior_snd_una))
+ continue;
- /* Event "B" in the comment above. */
- if (after(end_seq, tp->high_seq))
- flag |= FLAG_DATA_LOST;
+ used_sacks++;
+ }
- tcp_for_write_queue_from(skb, sk) {
- int in_sack = 0;
- u8 sacked;
+ /* order SACK blocks to allow in order walk of the retrans queue */
+ for (i = used_sacks - 1; i > 0; i--) {
+ for (j = 0; j < i; j++){
+ if (after(sp[j].start_seq, sp[j+1].start_seq)) {
+ struct tcp_sack_block tmp;
- if (skb == tcp_send_head(sk))
- break;
+ tmp = sp[j];
+ sp[j] = sp[j+1];
+ sp[j+1] = tmp;
- cached_skb = skb;
- cached_fack_count = fack_count;
- if (i == first_sack_index) {
- tp->fastpath_skb_hint = skb;
- tp->fastpath_cnt_hint = fack_count;
+ /* Track where the first SACK block goes to */
+ if (j == first_sack_index)
+ first_sack_index = j+1;
}
+ }
+ }
- /* The retransmission queue is always in order, so
- * we can short-circuit the walk early.
- */
- if (!before(TCP_SKB_CB(skb)->seq, end_seq))
- break;
+ skb = tcp_write_queue_head(sk);
+ fack_count = 0;
+ i = 0;
- dup_sack = (found_dup_sack && (i == first_sack_index));
+ if (!tp->sacked_out) {
+ /* It's already past, so skip checking against it */
+ cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
+ } else {
+ cache = tp->recv_sack_cache;
+ /* Skip empty blocks in at head of the cache */
+ while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq &&
+ !cache->end_seq)
+ cache++;
+ }
- /* Due to sorting DSACK may reside within this SACK block! */
- if (next_dup) {
- u32 dup_start = ntohl(sp->start_seq);
- u32 dup_end = ntohl(sp->end_seq);
+ while (i < used_sacks) {
+ u32 start_seq = sp[i].start_seq;
+ u32 end_seq = sp[i].end_seq;
+ int dup_sack = (found_dup_sack && (i == first_sack_index));
+ struct tcp_sack_block *next_dup = NULL;
- if (before(TCP_SKB_CB(skb)->seq, dup_end)) {
- in_sack = tcp_match_skb_to_sack(sk, skb, dup_start, dup_end);
- if (in_sack > 0)
- dup_sack = 1;
- }
- }
+ if (found_dup_sack && ((i + 1) == first_sack_index))
+ next_dup = &sp[i + 1];
- /* DSACK info lost if out-of-mem, try SACK still */
- if (in_sack <= 0)
- in_sack = tcp_match_skb_to_sack(sk, skb, start_seq, end_seq);
- if (unlikely(in_sack < 0))
- break;
+ /* Event "B" in the comment above. */
+ if (after(end_seq, tp->high_seq))
+ flag |= FLAG_DATA_LOST;
- if (!in_sack) {
- fack_count += tcp_skb_pcount(skb);
- continue;
+ /* Skip too early cached blocks */
+ while (tcp_sack_cache_ok(tp, cache) &&
+ !before(start_seq, cache->end_seq))
+ cache++;
+
+ /* Can skip some work by looking recv_sack_cache? */
+ if (tcp_sack_cache_ok(tp, cache) && !dup_sack &&
+ after(end_seq, cache->start_seq)) {
+
+ /* Head todo? */
+ if (before(start_seq, cache->start_seq)) {
+ skb = tcp_sacktag_skip(skb, sk, start_seq);
+ skb = tcp_sacktag_walk(skb, sk, next_dup, start_seq,
+ cache->start_seq, dup_sack,
+ &fack_count, &reord, &flag);
}
- sacked = TCP_SKB_CB(skb)->sacked;
-
- /* Account D-SACK for retransmitted packet. */
- if (dup_sack && (sacked & TCPCB_RETRANS)) {
- if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
- tp->undo_retrans--;
- if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una) &&
- (sacked & TCPCB_SACKED_ACKED))
- reord = min(fack_count, reord);
- }
+ /* Rest of the block already fully processed? */
+ if (!after(end_seq, cache->end_seq))
+ goto advance_sp;
+ skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, cache->end_seq,
+ &fack_count, &reord, &flag);
- /* Nothing to do; acked frame is about to be dropped (was ACKed). */
- if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
- fack_count += tcp_skb_pcount(skb);
- continue;
+ /* ...tail remains todo... */
+ if (TCP_SKB_CB(tp->highest_sack)->end_seq == cache->end_seq) {
+ /* ...but better entrypoint exists! */
+ skb = tcp_write_queue_next(sk, tp->highest_sack);
+ fack_count = tp->fackets_out;
+ cache++;
+ goto walk;
}
- if (!(sacked&TCPCB_SACKED_ACKED)) {
- if (sacked & TCPCB_SACKED_RETRANS) {
- /* If the segment is not tagged as lost,
- * we do not clear RETRANS, believing
- * that retransmission is still in flight.
- */
- if (sacked & TCPCB_LOST) {
- TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
- tp->lost_out -= tcp_skb_pcount(skb);
- tp->retrans_out -= tcp_skb_pcount(skb);
-
- /* clear lost hint */
- tp->retransmit_skb_hint = NULL;
- }
- } else {
- if (!(sacked & TCPCB_RETRANS)) {
- /* New sack for not retransmitted frame,
- * which was in hole. It is reordering.
- */
- if (before(TCP_SKB_CB(skb)->seq,
- tcp_highest_sack_seq(tp)))
- reord = min(fack_count, reord);
-
- /* SACK enhanced F-RTO (RFC4138; Appendix B) */
- if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
- flag |= FLAG_ONLY_ORIG_SACKED;
- }
-
- if (sacked & TCPCB_LOST) {
- TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
- tp->lost_out -= tcp_skb_pcount(skb);
-
- /* clear lost hint */
- tp->retransmit_skb_hint = NULL;
- }
- }
-
- TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
- flag |= FLAG_DATA_SACKED;
- tp->sacked_out += tcp_skb_pcount(skb);
-
- fack_count += tcp_skb_pcount(skb);
-
- /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
- if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
- before(TCP_SKB_CB(skb)->seq,
- TCP_SKB_CB(tp->lost_skb_hint)->seq))
- tp->lost_cnt_hint += tcp_skb_pcount(skb);
-
- if (fack_count > tp->fackets_out)
- tp->fackets_out = fack_count;
-
- if (after(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
- tp->highest_sack = skb;
-
- } else {
- if (dup_sack && (sacked&TCPCB_RETRANS))
- reord = min(fack_count, reord);
-
- fack_count += tcp_skb_pcount(skb);
- }
+ skb = tcp_sacktag_skip(skb, sk, cache->end_seq);
+ /* Check overlap against next cached too (past this one already) */
+ cache++;
+ continue;
+ }
- /* D-SACK. We can detect redundant retransmission
- * in S|R and plain R frames and clear it.
- * undo_retrans is decreased above, L|R frames
- * are accounted above as well.
- */
- if (dup_sack &&
- (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
- TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
- tp->retrans_out -= tcp_skb_pcount(skb);
- tp->retransmit_skb_hint = NULL;
- }
+ if (tp->sacked_out && !before(start_seq, tcp_highest_sack_seq(tp))) {
+ skb = tcp_write_queue_next(sk, tp->highest_sack);
+ fack_count = tp->fackets_out;
}
+ skb = tcp_sacktag_skip(skb, sk, start_seq);
+
+walk:
+ skb = tcp_sacktag_walk(skb, sk, next_dup, start_seq, end_seq,
+ dup_sack, &fack_count, &reord, &flag);
+advance_sp:
/* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
* due to in-order walk
*/
if (after(end_seq, tp->frto_highmark))
flag &= ~FLAG_ONLY_ORIG_SACKED;
+
+ i++;
+ }
+
+ /* Clear the head of the cache sack blocks so we can skip it next time */
+ for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) {
+ tp->recv_sack_cache[i].start_seq = 0;
+ tp->recv_sack_cache[i].end_seq = 0;
}
+ for (j = 0; j < used_sacks; j++)
+ tp->recv_sack_cache[i++] = sp[j];
- flag |= tcp_mark_lost_retrans(sk);
+ tcp_mark_lost_retrans(sk);
tcp_verify_left_out(tp);
}
tp->fackets_out -= min(pkts_acked, tp->fackets_out);
- /* hint's skb might be NULL but we don't need to care */
- tp->fastpath_cnt_hint -= min_t(u32, pkts_acked,
- tp->fastpath_cnt_hint);
+
if (ca_ops->pkts_acked) {
s32 rtt_us = -1;
/* Do not send POLL_HUP for half duplex close. */
if (sk->sk_shutdown == SHUTDOWN_MASK ||
sk->sk_state == TCP_CLOSE)
- sk_wake_async(sk, 1, POLL_HUP);
+ sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
else
- sk_wake_async(sk, 1, POLL_IN);
+ sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
}
}
if (!sock_flag(sk, SOCK_DEAD)) {
sk->sk_state_change(sk);
- sk_wake_async(sk, 0, POLL_OUT);
+ sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
}
if (sk->sk_write_pending ||
* are not waked up, because sk->sk_sleep ==
* NULL and sk->sk_socket == NULL.
*/
- if (sk->sk_socket) {
- sk_wake_async(sk,0,POLL_OUT);
- }
+ if (sk->sk_socket)
+ sk_wake_async(sk,
+ SOCK_WAKE_IO, POLL_OUT);
tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
tp->snd_wnd = ntohs(th->window) <<
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