/* People can turn this off for buggy TCP's found in printers etc. */
int sysctl_tcp_retrans_collapse = 1;
+/* This limits the percentage of the congestion window which we
+ * will allow a single TSO frame to consume. Building TSO frames
+ * which are too large can cause TCP streams to be bursty.
+ */
+int sysctl_tcp_tso_win_divisor = 8;
+
static __inline__
void update_send_head(struct sock *sk, struct tcp_opt *tp, struct sk_buff *skb)
{
if (sk->sk_send_head == (struct sk_buff *)&sk->sk_write_queue)
sk->sk_send_head = NULL;
tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
- if (tp->packets_out++ == 0)
- tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
+ tcp_packets_out_inc(sk, tp, skb);
}
/* SND.NXT, if window was not shrunk.
{
u32 now = tcp_time_stamp;
- if (!tp->packets_out && (s32)(now - tp->lsndtime) > tp->rto)
+ if (!tcp_get_pcount(&tp->packets_out) &&
+ (s32)(now - tp->lsndtime) > tp->rto)
tcp_cwnd_restart(tp, __sk_dst_get(sk));
tp->lsndtime = now;
tcp_clear_xmit_timer(sk, TCP_TIME_DACK);
}
+/* Determine a window scaling and initial window to offer.
+ * Based on the assumption that the given amount of space
+ * will be offered. Store the results in the tp structure.
+ * NOTE: for smooth operation initial space offering should
+ * be a multiple of mss if possible. We assume here that mss >= 1.
+ * This MUST be enforced by all callers.
+ */
+void tcp_select_initial_window(int __space, __u32 mss,
+ __u32 *rcv_wnd, __u32 *window_clamp,
+ int wscale_ok, __u8 *rcv_wscale)
+{
+ unsigned int space = (__space < 0 ? 0 : __space);
+
+ /* If no clamp set the clamp to the max possible scaled window */
+ if (*window_clamp == 0)
+ (*window_clamp) = (65535 << 14);
+ space = min(*window_clamp, space);
+
+ /* Quantize space offering to a multiple of mss if possible. */
+ if (space > mss)
+ space = (space / mss) * mss;
+
+ /* NOTE: offering an initial window larger than 32767
+ * will break some buggy TCP stacks. We try to be nice.
+ * If we are not window scaling, then this truncates
+ * our initial window offering to 32k. There should also
+ * be a sysctl option to stop being nice.
+ */
+ (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
+ (*rcv_wscale) = 0;
+ if (wscale_ok) {
+ /* Set window scaling on max possible window
+ * See RFC1323 for an explanation of the limit to 14
+ */
+ space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
+ while (space > 65535 && (*rcv_wscale) < 14) {
+ space >>= 1;
+ (*rcv_wscale)++;
+ }
+ }
+
+ /* Set initial window to value enough for senders,
+ * following RFC1414. Senders, not following this RFC,
+ * will be satisfied with 2.
+ */
+ if (mss > (1<<*rcv_wscale)) {
+ int init_cwnd = 4;
+ if (mss > 1460*3)
+ init_cwnd = 2;
+ else if (mss > 1460)
+ init_cwnd = 3;
+ if (*rcv_wnd > init_cwnd*mss)
+ *rcv_wnd = init_cwnd*mss;
+ }
+
+ /* Set the clamp no higher than max representable value */
+ (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
+}
+
/* Chose a new window to advertise, update state in tcp_opt for the
* socket, and return result with RFC1323 scaling applied. The return
* value can be stuffed directly into th->window for an outgoing
* We are working here with either a clone of the original
* SKB, or a fresh unique copy made by the retransmit engine.
*/
-int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb)
+static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb)
{
- if(skb != NULL) {
+ if (skb != NULL) {
struct inet_opt *inet = inet_sk(sk);
struct tcp_opt *tp = tcp_sk(sk);
struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
int sysctl_flags;
int err;
+ BUG_ON(!tcp_skb_pcount(skb));
+
#define SYSCTL_FLAG_TSTAMPS 0x1
#define SYSCTL_FLAG_WSCALE 0x2
#define SYSCTL_FLAG_SACK 0x4
if (!tcp_transmit_skb(sk, skb_clone(skb, sk->sk_allocation))) {
sk->sk_send_head = NULL;
tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
- if (tp->packets_out++ == 0)
- tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
+ tcp_packets_out_inc(sk, tp, skb);
return;
}
}
}
+void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_std)
+{
+ if (skb->len <= mss_std) {
+ /* Avoid the costly divide in the normal
+ * non-TSO case.
+ */
+ skb_shinfo(skb)->tso_segs = 1;
+ skb_shinfo(skb)->tso_size = 0;
+ } else {
+ unsigned int factor;
+
+ factor = skb->len + (mss_std - 1);
+ factor /= mss_std;
+ skb_shinfo(skb)->tso_segs = factor;
+ skb_shinfo(skb)->tso_size = mss_std;
+ }
+}
+
/* Function to create two new TCP segments. Shrinks the given segment
* to the specified size and appends a new segment with the rest of the
* packet to the list. This won't be called frequently, I hope.
flags = TCP_SKB_CB(skb)->flags;
TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
TCP_SKB_CB(buff)->flags = flags;
- TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_EVER_RETRANS|TCPCB_AT_TAIL);
- if (TCP_SKB_CB(buff)->sacked&TCPCB_LOST) {
- tp->lost_out++;
- tp->left_out++;
- }
+ TCP_SKB_CB(buff)->sacked =
+ (TCP_SKB_CB(skb)->sacked &
+ (TCPCB_LOST | TCPCB_EVER_RETRANS | TCPCB_AT_TAIL));
TCP_SKB_CB(skb)->sacked &= ~TCPCB_AT_TAIL;
if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_HW) {
*/
TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
+ tcp_dec_pcount(&tp->lost_out, skb);
+ tcp_dec_pcount(&tp->left_out, skb);
+ }
+
+ /* Fix up tso_factor for both original and new SKB. */
+ tcp_set_skb_tso_segs(skb, tp->mss_cache_std);
+ tcp_set_skb_tso_segs(buff, tp->mss_cache_std);
+
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
+ tcp_inc_pcount(&tp->lost_out, skb);
+ tcp_inc_pcount(&tp->left_out, skb);
+ }
+
+ if (TCP_SKB_CB(buff)->sacked&TCPCB_LOST) {
+ tcp_inc_pcount(&tp->lost_out, buff);
+ tcp_inc_pcount(&tp->left_out, buff);
+ }
+
/* Link BUFF into the send queue. */
__skb_append(skb, buff);
* eventually). The difference is that pulled data not copied, but
* immediately discarded.
*/
-unsigned char * __pskb_trim_head(struct sk_buff *skb, int len)
+static unsigned char *__pskb_trim_head(struct sk_buff *skb, int len)
{
int i, k, eat;
return skb->tail;
}
-static int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
+int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
+ struct tcp_opt *tp = tcp_sk(sk);
+
if (skb_cloned(skb) &&
pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
return -ENOMEM;
TCP_SKB_CB(skb)->seq += len;
skb->ip_summed = CHECKSUM_HW;
+
+ skb->truesize -= len;
+ sk->sk_queue_shrunk = 1;
+ sk->sk_wmem_queued -= len;
+ sk->sk_forward_alloc += len;
+
+ /* Any change of skb->len requires recalculation of tso
+ * factor and mss.
+ */
+ tcp_set_skb_tso_segs(skb, tp->mss_cache_std);
+
return 0;
}
this function. --ANK (980731)
*/
-int tcp_sync_mss(struct sock *sk, u32 pmtu)
+unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
struct tcp_opt *tp = tcp_sk(sk);
struct dst_entry *dst = __sk_dst_get(sk);
tp->pmtu_cookie = pmtu;
tp->mss_cache = tp->mss_cache_std = mss_now;
- if (sk->sk_route_caps & NETIF_F_TSO) {
- int large_mss;
+ return mss_now;
+}
+
+/* Compute the current effective MSS, taking SACKs and IP options,
+ * and even PMTU discovery events into account.
+ *
+ * LARGESEND note: !urg_mode is overkill, only frames up to snd_up
+ * cannot be large. However, taking into account rare use of URG, this
+ * is not a big flaw.
+ */
+
+unsigned int tcp_current_mss(struct sock *sk, int large)
+{
+ struct tcp_opt *tp = tcp_sk(sk);
+ struct dst_entry *dst = __sk_dst_get(sk);
+ unsigned int do_large, mss_now;
+
+ mss_now = tp->mss_cache_std;
+ if (dst) {
+ u32 mtu = dst_pmtu(dst);
+ if (mtu != tp->pmtu_cookie ||
+ tp->ext2_header_len != dst->header_len)
+ mss_now = tcp_sync_mss(sk, mtu);
+ }
+
+ do_large = (large &&
+ (sk->sk_route_caps & NETIF_F_TSO) &&
+ !tp->urg_mode);
+
+ if (do_large) {
+ unsigned int large_mss, factor, limit;
large_mss = 65535 - tp->af_specific->net_header_len -
- tp->ext_header_len - tp->ext2_header_len - tp->tcp_header_len;
+ tp->ext_header_len - tp->ext2_header_len -
+ tp->tcp_header_len;
if (tp->max_window && large_mss > (tp->max_window>>1))
- large_mss = max((tp->max_window>>1), 68U - tp->tcp_header_len);
+ large_mss = max((tp->max_window>>1),
+ 68U - tp->tcp_header_len);
+
+ factor = large_mss / mss_now;
- /* Always keep large mss multiple of real mss. */
- tp->mss_cache = mss_now*(large_mss/mss_now);
+ /* Always keep large mss multiple of real mss, but
+ * do not exceed 1/tso_win_divisor of the congestion window
+ * so we can keep the ACK clock ticking and minimize
+ * bursting.
+ */
+ limit = tp->snd_cwnd;
+ if (sysctl_tcp_tso_win_divisor)
+ limit /= sysctl_tcp_tso_win_divisor;
+ limit = max(1U, limit);
+ if (factor > limit)
+ factor = limit;
+
+ tp->mss_cache = mss_now * factor;
+
+ mss_now = tp->mss_cache;
}
+ if (tp->eff_sacks)
+ mss_now -= (TCPOLEN_SACK_BASE_ALIGNED +
+ (tp->eff_sacks * TCPOLEN_SACK_PERBLOCK));
return mss_now;
}
-
/* This routine writes packets to the network. It advances the
* send_head. This happens as incoming acks open up the remote
* window for us.
TCP_SKB_CB(skb)->when = tcp_time_stamp;
if (tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC)))
break;
- /* Advance the send_head. This one is sent out. */
+
+ /* Advance the send_head. This one is sent out.
+ * This call will increment packets_out.
+ */
update_send_head(sk, tp, skb);
+
tcp_minshall_update(tp, mss_now, skb);
sent_pkts = 1;
}
return 0;
}
- return !tp->packets_out && sk->sk_send_head;
+ return !tcp_get_pcount(&tp->packets_out) && sk->sk_send_head;
}
return 0;
}
/* The first test we must make is that neither of these two
* SKB's are still referenced by someone else.
*/
- if(!skb_cloned(skb) && !skb_cloned(next_skb)) {
+ if (!skb_cloned(skb) && !skb_cloned(next_skb)) {
int skb_size = skb->len, next_skb_size = next_skb->len;
u16 flags = TCP_SKB_CB(skb)->flags;
((skb_size + next_skb_size) > mss_now))
return;
+ BUG_ON(tcp_skb_pcount(skb) != 1 ||
+ tcp_skb_pcount(next_skb) != 1);
+
/* Ok. We will be able to collapse the packet. */
__skb_unlink(next_skb, next_skb->list);
*/
TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked&(TCPCB_EVER_RETRANS|TCPCB_AT_TAIL);
if (TCP_SKB_CB(next_skb)->sacked&TCPCB_SACKED_RETRANS)
- tp->retrans_out--;
+ tcp_dec_pcount(&tp->retrans_out, next_skb);
if (TCP_SKB_CB(next_skb)->sacked&TCPCB_LOST) {
- tp->lost_out--;
- tp->left_out--;
+ tcp_dec_pcount(&tp->lost_out, next_skb);
+ tcp_dec_pcount(&tp->left_out, next_skb);
}
/* Reno case is special. Sigh... */
- if (!tp->sack_ok && tp->sacked_out) {
- tp->sacked_out--;
- tp->left_out--;
+ if (!tp->sack_ok && tcp_get_pcount(&tp->sacked_out)) {
+ tcp_dec_pcount_approx(&tp->sacked_out, next_skb);
+ tcp_dec_pcount(&tp->left_out, next_skb);
}
/* Not quite right: it can be > snd.fack, but
* it is better to underestimate fackets.
*/
- if (tp->fackets_out)
- tp->fackets_out--;
+ tcp_dec_pcount_approx(&tp->fackets_out, next_skb);
+ tcp_packets_out_dec(tp, next_skb);
sk_stream_free_skb(sk, next_skb);
- tp->packets_out--;
}
}
!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) {
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
- tp->retrans_out--;
+ tcp_dec_pcount(&tp->retrans_out, skb);
}
if (!(TCP_SKB_CB(skb)->sacked&TCPCB_LOST)) {
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
- tp->lost_out++;
+ tcp_inc_pcount(&tp->lost_out, skb);
lost = 1;
}
}
&& TCP_SKB_CB(skb)->seq != tp->snd_una)
return -EAGAIN;
- if(skb->len > cur_mss) {
- if(tcp_fragment(sk, skb, cur_mss))
+ if (skb->len > cur_mss) {
+ int old_factor = tcp_skb_pcount(skb);
+ int new_factor;
+
+ if (tcp_fragment(sk, skb, cur_mss))
return -ENOMEM; /* We'll try again later. */
/* New SKB created, account for it. */
- tp->packets_out++;
+ new_factor = tcp_skb_pcount(skb);
+ tcp_dec_pcount_explicit(&tp->packets_out,
+ old_factor - new_factor);
+ tcp_inc_pcount(&tp->packets_out, skb->next);
}
/* Collapse two adjacent packets if worthwhile and we can. */
tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) {
if (!pskb_trim(skb, 0)) {
TCP_SKB_CB(skb)->seq = TCP_SKB_CB(skb)->end_seq - 1;
+ skb_shinfo(skb)->tso_segs = 1;
+ skb_shinfo(skb)->tso_size = 0;
skb->ip_summed = CHECKSUM_NONE;
skb->csum = 0;
}
}
#endif
TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
- tp->retrans_out++;
+ tcp_inc_pcount(&tp->retrans_out, skb);
/* Save stamp of the first retransmit. */
if (!tp->retrans_stamp)
{
struct tcp_opt *tp = tcp_sk(sk);
struct sk_buff *skb;
- int packet_cnt = tp->lost_out;
+ int packet_cnt = tcp_get_pcount(&tp->lost_out);
/* First pass: retransmit lost packets. */
if (packet_cnt) {
sk_stream_for_retrans_queue(skb, sk) {
__u8 sacked = TCP_SKB_CB(skb)->sacked;
+ /* Assume this retransmit will generate
+ * only one packet for congestion window
+ * calculation purposes. This works because
+ * tcp_retransmit_skb() will chop up the
+ * packet to be MSS sized and all the
+ * packet counting works out.
+ */
if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
return;
tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
}
- if (--packet_cnt <= 0)
+ packet_cnt -= tcp_skb_pcount(skb);
+ if (packet_cnt <= 0)
break;
}
}
/* Yeah, we have to make difficult choice between forward transmission
* and retransmission... Both ways have their merits...
*
- * For now we do not retrnamsit anything, while we have some new
+ * For now we do not retransmit anything, while we have some new
* segments to send.
*/
packet_cnt = 0;
sk_stream_for_retrans_queue(skb, sk) {
- if(++packet_cnt > tp->fackets_out)
+ /* Similar to the retransmit loop above we
+ * can pretend that the retransmitted SKB
+ * we send out here will be composed of one
+ * real MSS sized packet because tcp_retransmit_skb()
+ * will fragment it if necessary.
+ */
+ if (++packet_cnt > tcp_get_pcount(&tp->fackets_out))
break;
if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
break;
- if(TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS)
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS)
continue;
/* Ok, retransmit it. */
- if(tcp_retransmit_skb(sk, skb))
+ if (tcp_retransmit_skb(sk, skb))
break;
if (skb == skb_peek(&sk->sk_write_queue))
{
struct tcp_opt *tp = tcp_sk(sk);
struct sk_buff *skb = skb_peek_tail(&sk->sk_write_queue);
- unsigned int mss_now;
+ int mss_now;
/* Optimization, tack on the FIN if we have a queue of
* unsent frames. But be careful about outgoing SACKS
* and IP options.
*/
- mss_now = tcp_current_mss(sk, 1);
+ mss_now = tcp_current_mss(sk, 1);
if (sk->sk_send_head != NULL) {
TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN;
skb->csum = 0;
TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_FIN);
TCP_SKB_CB(skb)->sacked = 0;
+ skb_shinfo(skb)->tso_segs = 1;
+ skb_shinfo(skb)->tso_size = 0;
/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
TCP_SKB_CB(skb)->seq = tp->write_seq;
skb->csum = 0;
TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_RST);
TCP_SKB_CB(skb)->sacked = 0;
+ skb_shinfo(skb)->tso_segs = 1;
+ skb_shinfo(skb)->tso_size = 0;
/* Send it off. */
TCP_SKB_CB(skb)->seq = tcp_acceptable_seq(sk, tp);
th->dest = req->rmt_port;
TCP_SKB_CB(skb)->seq = req->snt_isn;
TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1;
+ TCP_SKB_CB(skb)->sacked = 0;
+ skb_shinfo(skb)->tso_segs = 1;
+ skb_shinfo(skb)->tso_size = 0;
th->seq = htonl(TCP_SKB_CB(skb)->seq);
th->ack_seq = htonl(req->rcv_isn + 1);
if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
tp->advmss = dst_metric(dst, RTAX_ADVMSS);
tcp_initialize_rcv_mss(sk);
- tcp_vegas_init(tp);
+ tcp_ca_init(tp);
tcp_select_initial_window(tcp_full_space(sk),
tp->advmss - (tp->ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
TCP_SKB_CB(buff)->flags = TCPCB_FLAG_SYN;
TCP_ECN_send_syn(sk, tp, buff);
TCP_SKB_CB(buff)->sacked = 0;
+ skb_shinfo(buff)->tso_segs = 1;
+ skb_shinfo(buff)->tso_size = 0;
buff->csum = 0;
TCP_SKB_CB(buff)->seq = tp->write_seq++;
TCP_SKB_CB(buff)->end_seq = tp->write_seq;
tp->snd_nxt = tp->write_seq;
tp->pushed_seq = tp->write_seq;
- tcp_vegas_init(tp);
+ tcp_ca_init(tp);
/* Send it off. */
TCP_SKB_CB(buff)->when = tcp_time_stamp;
tp->retrans_stamp = TCP_SKB_CB(buff)->when;
__skb_queue_tail(&sk->sk_write_queue, buff);
sk_charge_skb(sk, buff);
- tp->packets_out++;
+ tcp_inc_pcount(&tp->packets_out, buff);
tcp_transmit_skb(sk, skb_clone(buff, GFP_KERNEL));
TCP_INC_STATS(TCP_MIB_ACTIVEOPENS);
buff->csum = 0;
TCP_SKB_CB(buff)->flags = TCPCB_FLAG_ACK;
TCP_SKB_CB(buff)->sacked = 0;
+ skb_shinfo(buff)->tso_segs = 1;
+ skb_shinfo(buff)->tso_size = 0;
/* Send it off, this clears delayed acks for us. */
TCP_SKB_CB(buff)->seq = TCP_SKB_CB(buff)->end_seq = tcp_acceptable_seq(sk, tp);
skb->csum = 0;
TCP_SKB_CB(skb)->flags = TCPCB_FLAG_ACK;
TCP_SKB_CB(skb)->sacked = urgent;
+ skb_shinfo(skb)->tso_segs = 1;
+ skb_shinfo(skb)->tso_size = 0;
/* Use a previous sequence. This should cause the other
* end to send an ack. Don't queue or clone SKB, just
if ((skb = sk->sk_send_head) != NULL &&
before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)) {
int err;
- int mss = tcp_current_mss(sk, 0);
- int seg_size = tp->snd_una+tp->snd_wnd-TCP_SKB_CB(skb)->seq;
+ unsigned int mss = tcp_current_mss(sk, 0);
+ unsigned int seg_size = tp->snd_una+tp->snd_wnd-TCP_SKB_CB(skb)->seq;
if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
sk->sk_route_caps &= ~NETIF_F_TSO;
tp->mss_cache = tp->mss_cache_std;
}
- }
+ } else if (!tcp_skb_pcount(skb))
+ tcp_set_skb_tso_segs(skb, tp->mss_cache_std);
+
TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
TCP_SKB_CB(skb)->when = tcp_time_stamp;
err = tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC));
err = tcp_write_wakeup(sk);
- if (tp->packets_out || !sk->sk_send_head) {
+ if (tcp_get_pcount(&tp->packets_out) || !sk->sk_send_head) {
/* Cancel probe timer, if it is not required. */
tp->probes_out = 0;
tp->backoff = 0;
EXPORT_SYMBOL(tcp_send_synack);
EXPORT_SYMBOL(tcp_simple_retransmit);
EXPORT_SYMBOL(tcp_sync_mss);
-EXPORT_SYMBOL(tcp_transmit_skb);
EXPORT_SYMBOL(tcp_write_wakeup);
EXPORT_SYMBOL(tcp_write_xmit);