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Merge branch 'sctp-Introduce-sctp_flush_ctx'

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Marcelo Ricardo Leitner says:

====================
sctp: Introduce sctp_flush_ctx

This struct will hold all the context used during the outq flush, so we
don't have to pass lots of pointers all around.

Checked on x86_64, the compiler inlines all these functions and there is no
derreference added because of the struct.

This patchset depends on 'sctp: refactor sctp_outq_flush'

Changes since v1:
- updated to build on top of v2 of 'sctp: refactor sctp_outq_flush'

Changes since v2:
- fixed a rebase issue which reverted a change in patch 2.
- rebased on v3 of 'sctp: refactor sctp_outq_flush'
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2018-05-14 23:15:27 -04:00
commit 961423f9fc
1 changed files with 116 additions and 137 deletions
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253
net/sctp/outqueue.c
View File

@ -791,19 +791,28 @@ static int sctp_packet_singleton(struct sctp_transport *transport,
return sctp_packet_transmit(&singleton, gfp); return sctp_packet_transmit(&singleton, gfp);
} }
static bool sctp_outq_select_transport(struct sctp_chunk *chunk, /* Struct to hold the context during sctp outq flush */
struct sctp_association *asoc, struct sctp_flush_ctx {
struct sctp_transport **transport, struct sctp_outq *q;
struct list_head *transport_list) /* Current transport being used. It's NOT the same as curr active one */
struct sctp_transport *transport;
/* These transports have chunks to send. */
struct list_head transport_list;
struct sctp_association *asoc;
/* Packet on the current transport above */
struct sctp_packet *packet;
gfp_t gfp;
};
/* transport: current transport */
static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
struct sctp_chunk *chunk)
{ {
struct sctp_transport *new_transport = chunk->transport; struct sctp_transport *new_transport = chunk->transport;
struct sctp_transport *curr = *transport;
bool changed = false;
if (!new_transport) { if (!new_transport) {
if (!sctp_chunk_is_data(chunk)) { if (!sctp_chunk_is_data(chunk)) {
/* /* If we have a prior transport pointer, see if
* If we have a prior transport pointer, see if
* the destination address of the chunk * the destination address of the chunk
* matches the destination address of the * matches the destination address of the
* current transport. If not a match, then * current transport. If not a match, then
@ -812,11 +821,11 @@ static bool sctp_outq_select_transport(struct sctp_chunk *chunk,
* after processing ASCONFs, we may have new * after processing ASCONFs, we may have new
* transports created. * transports created.
*/ */
if (curr && sctp_cmp_addr_exact(&chunk->dest, if (ctx->transport && sctp_cmp_addr_exact(&chunk->dest,
&curr->ipaddr)) &ctx->transport->ipaddr))
new_transport = curr; new_transport = ctx->transport;
else else
new_transport = sctp_assoc_lookup_paddr(asoc, new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
&chunk->dest); &chunk->dest);
} }
@ -824,7 +833,7 @@ static bool sctp_outq_select_transport(struct sctp_chunk *chunk,
* use the current active path. * use the current active path.
*/ */
if (!new_transport) if (!new_transport)
new_transport = asoc->peer.active_path; new_transport = ctx->asoc->peer.active_path;
} else { } else {
__u8 type; __u8 type;
@ -849,7 +858,7 @@ static bool sctp_outq_select_transport(struct sctp_chunk *chunk,
if (type != SCTP_CID_HEARTBEAT && if (type != SCTP_CID_HEARTBEAT &&
type != SCTP_CID_HEARTBEAT_ACK && type != SCTP_CID_HEARTBEAT_ACK &&
type != SCTP_CID_ASCONF_ACK) type != SCTP_CID_ASCONF_ACK)
new_transport = asoc->peer.active_path; new_transport = ctx->asoc->peer.active_path;
break; break;
default: default:
break; break;
@ -857,37 +866,31 @@ static bool sctp_outq_select_transport(struct sctp_chunk *chunk,
} }
/* Are we switching transports? Take care of transport locks. */ /* Are we switching transports? Take care of transport locks. */
if (new_transport != curr) { if (new_transport != ctx->transport) {
changed = true; ctx->transport = new_transport;
curr = new_transport; ctx->packet = &ctx->transport->packet;
*transport = curr;
if (list_empty(&curr->send_ready))
list_add_tail(&curr->send_ready, transport_list);
sctp_packet_config(&curr->packet, asoc->peer.i.init_tag, if (list_empty(&ctx->transport->send_ready))
asoc->peer.ecn_capable); list_add_tail(&ctx->transport->send_ready,
&ctx->transport_list);
sctp_packet_config(ctx->packet,
ctx->asoc->peer.i.init_tag,
ctx->asoc->peer.ecn_capable);
/* We've switched transports, so apply the /* We've switched transports, so apply the
* Burst limit to the new transport. * Burst limit to the new transport.
*/ */
sctp_transport_burst_limited(curr); sctp_transport_burst_limited(ctx->transport);
} }
return changed;
} }
static void sctp_outq_flush_ctrl(struct sctp_outq *q, static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
struct sctp_transport **_transport,
struct list_head *transport_list,
gfp_t gfp)
{ {
struct sctp_transport *transport = *_transport;
struct sctp_association *asoc = q->asoc;
struct sctp_packet *packet = NULL;
struct sctp_chunk *chunk, *tmp; struct sctp_chunk *chunk, *tmp;
enum sctp_xmit status; enum sctp_xmit status;
int one_packet, error; int one_packet, error;
list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) { list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
one_packet = 0; one_packet = 0;
/* RFC 5061, 5.3 /* RFC 5061, 5.3
@ -896,7 +899,7 @@ static void sctp_outq_flush_ctrl(struct sctp_outq *q,
* NOT use the new IP address as a source for ANY SCTP * NOT use the new IP address as a source for ANY SCTP
* packet except on carrying an ASCONF Chunk. * packet except on carrying an ASCONF Chunk.
*/ */
if (asoc->src_out_of_asoc_ok && if (ctx->asoc->src_out_of_asoc_ok &&
chunk->chunk_hdr->type != SCTP_CID_ASCONF) chunk->chunk_hdr->type != SCTP_CID_ASCONF)
continue; continue;
@ -905,15 +908,10 @@ static void sctp_outq_flush_ctrl(struct sctp_outq *q,
/* Pick the right transport to use. Should always be true for /* Pick the right transport to use. Should always be true for
* the first chunk as we don't have a transport by then. * the first chunk as we don't have a transport by then.
*/ */
if (sctp_outq_select_transport(chunk, asoc, _transport, sctp_outq_select_transport(ctx, chunk);
transport_list)) {
transport = *_transport;
packet = &transport->packet;
}
switch (chunk->chunk_hdr->type) { switch (chunk->chunk_hdr->type) {
/* /* 6.10 Bundling
* 6.10 Bundling
* ... * ...
* An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN * An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
* COMPLETE with any other chunks. [Send them immediately.] * COMPLETE with any other chunks. [Send them immediately.]
@ -921,16 +919,17 @@ static void sctp_outq_flush_ctrl(struct sctp_outq *q,
case SCTP_CID_INIT: case SCTP_CID_INIT:
case SCTP_CID_INIT_ACK: case SCTP_CID_INIT_ACK:
case SCTP_CID_SHUTDOWN_COMPLETE: case SCTP_CID_SHUTDOWN_COMPLETE:
error = sctp_packet_singleton(transport, chunk, gfp); error = sctp_packet_singleton(ctx->transport, chunk,
ctx->gfp);
if (error < 0) { if (error < 0) {
asoc->base.sk->sk_err = -error; ctx->asoc->base.sk->sk_err = -error;
return; return;
} }
break; break;
case SCTP_CID_ABORT: case SCTP_CID_ABORT:
if (sctp_test_T_bit(chunk)) if (sctp_test_T_bit(chunk))
packet->vtag = asoc->c.my_vtag; ctx->packet->vtag = ctx->asoc->c.my_vtag;
/* fallthru */ /* fallthru */
/* The following chunks are "response" chunks, i.e. /* The following chunks are "response" chunks, i.e.
@ -956,27 +955,27 @@ static void sctp_outq_flush_ctrl(struct sctp_outq *q,
case SCTP_CID_FWD_TSN: case SCTP_CID_FWD_TSN:
case SCTP_CID_I_FWD_TSN: case SCTP_CID_I_FWD_TSN:
case SCTP_CID_RECONF: case SCTP_CID_RECONF:
status = sctp_packet_transmit_chunk(packet, chunk, status = sctp_packet_transmit_chunk(ctx->packet, chunk,
one_packet, gfp); one_packet, ctx->gfp);
if (status != SCTP_XMIT_OK) { if (status != SCTP_XMIT_OK) {
/* put the chunk back */ /* put the chunk back */
list_add(&chunk->list, &q->control_chunk_list); list_add(&chunk->list, &ctx->q->control_chunk_list);
break; break;
} }
asoc->stats.octrlchunks++; ctx->asoc->stats.octrlchunks++;
/* PR-SCTP C5) If a FORWARD TSN is sent, the /* PR-SCTP C5) If a FORWARD TSN is sent, the
* sender MUST assure that at least one T3-rtx * sender MUST assure that at least one T3-rtx
* timer is running. * timer is running.
*/ */
if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN || if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) { chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
sctp_transport_reset_t3_rtx(transport); sctp_transport_reset_t3_rtx(ctx->transport);
transport->last_time_sent = jiffies; ctx->transport->last_time_sent = jiffies;
} }
if (chunk == asoc->strreset_chunk) if (chunk == ctx->asoc->strreset_chunk)
sctp_transport_reset_reconf_timer(transport); sctp_transport_reset_reconf_timer(ctx->transport);
break; break;
@ -988,76 +987,65 @@ static void sctp_outq_flush_ctrl(struct sctp_outq *q,
} }
/* Returns false if new data shouldn't be sent */ /* Returns false if new data shouldn't be sent */
static bool sctp_outq_flush_rtx(struct sctp_outq *q, static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
struct sctp_transport **_transport, int rtx_timeout)
struct list_head *transport_list,
int rtx_timeout, gfp_t gfp)
{ {
struct sctp_transport *transport = *_transport;
struct sctp_packet *packet = transport ? &transport->packet : NULL;
struct sctp_association *asoc = q->asoc;
int error, start_timer = 0; int error, start_timer = 0;
if (asoc->peer.retran_path->state == SCTP_UNCONFIRMED) if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
return false; return false;
if (transport != asoc->peer.retran_path) { if (ctx->transport != ctx->asoc->peer.retran_path) {
/* Switch transports & prepare the packet. */ /* Switch transports & prepare the packet. */
transport = asoc->peer.retran_path; ctx->transport = ctx->asoc->peer.retran_path;
*_transport = transport; ctx->packet = &ctx->transport->packet;
if (list_empty(&transport->send_ready)) if (list_empty(&ctx->transport->send_ready))
list_add_tail(&transport->send_ready, list_add_tail(&ctx->transport->send_ready,
transport_list); &ctx->transport_list);
packet = &transport->packet; sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag,
sctp_packet_config(packet, asoc->peer.i.init_tag, ctx->asoc->peer.ecn_capable);
asoc->peer.ecn_capable);
} }
error = __sctp_outq_flush_rtx(q, packet, rtx_timeout, &start_timer, error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout,
gfp); &start_timer, ctx->gfp);
if (error < 0) if (error < 0)
asoc->base.sk->sk_err = -error; ctx->asoc->base.sk->sk_err = -error;
if (start_timer) { if (start_timer) {
sctp_transport_reset_t3_rtx(transport); sctp_transport_reset_t3_rtx(ctx->transport);
transport->last_time_sent = jiffies; ctx->transport->last_time_sent = jiffies;
} }
/* This can happen on COOKIE-ECHO resend. Only /* This can happen on COOKIE-ECHO resend. Only
* one chunk can get bundled with a COOKIE-ECHO. * one chunk can get bundled with a COOKIE-ECHO.
*/ */
if (packet->has_cookie_echo) if (ctx->packet->has_cookie_echo)
return false; return false;
/* Don't send new data if there is still data /* Don't send new data if there is still data
* waiting to retransmit. * waiting to retransmit.
*/ */
if (!list_empty(&q->retransmit)) if (!list_empty(&ctx->q->retransmit))
return false; return false;
return true; return true;
} }
static void sctp_outq_flush_data(struct sctp_outq *q, static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
struct sctp_transport **_transport, int rtx_timeout)
struct list_head *transport_list,
int rtx_timeout, gfp_t gfp)
{ {
struct sctp_transport *transport = *_transport;
struct sctp_packet *packet = transport ? &transport->packet : NULL;
struct sctp_association *asoc = q->asoc;
struct sctp_chunk *chunk; struct sctp_chunk *chunk;
enum sctp_xmit status; enum sctp_xmit status;
/* Is it OK to send data chunks? */ /* Is it OK to send data chunks? */
switch (asoc->state) { switch (ctx->asoc->state) {
case SCTP_STATE_COOKIE_ECHOED: case SCTP_STATE_COOKIE_ECHOED:
/* Only allow bundling when this packet has a COOKIE-ECHO /* Only allow bundling when this packet has a COOKIE-ECHO
* chunk. * chunk.
*/ */
if (!packet || !packet->has_cookie_echo) if (!ctx->packet || !ctx->packet->has_cookie_echo)
return; return;
/* fallthru */ /* fallthru */
@ -1071,8 +1059,7 @@ static void sctp_outq_flush_data(struct sctp_outq *q,
return; return;
} }
/* /* RFC 2960 6.1 Transmission of DATA Chunks
* RFC 2960 6.1 Transmission of DATA Chunks
* *
* C) When the time comes for the sender to transmit, * C) When the time comes for the sender to transmit,
* before sending new DATA chunks, the sender MUST * before sending new DATA chunks, the sender MUST
@ -1080,56 +1067,47 @@ static void sctp_outq_flush_data(struct sctp_outq *q,
* are marked for retransmission (limited by the * are marked for retransmission (limited by the
* current cwnd). * current cwnd).
*/ */
if (!list_empty(&q->retransmit)) { if (!list_empty(&ctx->q->retransmit) &&
if (!sctp_outq_flush_rtx(q, _transport, transport_list, !sctp_outq_flush_rtx(ctx, rtx_timeout))
rtx_timeout, gfp)) return;
return;
/* We may have switched current transport */
transport = *_transport;
packet = &transport->packet;
}
/* Apply Max.Burst limitation to the current transport in /* Apply Max.Burst limitation to the current transport in
* case it will be used for new data. We are going to * case it will be used for new data. We are going to
* rest it before we return, but we want to apply the limit * rest it before we return, but we want to apply the limit
* to the currently queued data. * to the currently queued data.
*/ */
if (transport) if (ctx->transport)
sctp_transport_burst_limited(transport); sctp_transport_burst_limited(ctx->transport);
/* Finally, transmit new packets. */ /* Finally, transmit new packets. */
while ((chunk = sctp_outq_dequeue_data(q)) != NULL) { while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) {
__u32 sid = ntohs(chunk->subh.data_hdr->stream); __u32 sid = ntohs(chunk->subh.data_hdr->stream);
/* Has this chunk expired? */ /* Has this chunk expired? */
if (sctp_chunk_abandoned(chunk)) { if (sctp_chunk_abandoned(chunk)) {
sctp_sched_dequeue_done(q, chunk); sctp_sched_dequeue_done(ctx->q, chunk);
sctp_chunk_fail(chunk, 0); sctp_chunk_fail(chunk, 0);
sctp_chunk_free(chunk); sctp_chunk_free(chunk);
continue; continue;
} }
if (asoc->stream.out[sid].state == SCTP_STREAM_CLOSED) { if (ctx->asoc->stream.out[sid].state == SCTP_STREAM_CLOSED) {
sctp_outq_head_data(q, chunk); sctp_outq_head_data(ctx->q, chunk);
break; break;
} }
if (sctp_outq_select_transport(chunk, asoc, _transport, sctp_outq_select_transport(ctx, chunk);
transport_list)) {
transport = *_transport;
packet = &transport->packet;
}
pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p " pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
"skb->users:%d\n", __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
__func__, q, chunk, chunk && chunk->chunk_hdr ?
sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) : sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
"illegal chunk", ntohl(chunk->subh.data_hdr->tsn), "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
chunk->skb ? chunk->skb->head : NULL, chunk->skb ? chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
refcount_read(&chunk->skb->users) : -1); refcount_read(&chunk->skb->users) : -1);
/* Add the chunk to the packet. */ /* Add the chunk to the packet. */
status = sctp_packet_transmit_chunk(packet, chunk, 0, gfp); status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0,
ctx->gfp);
if (status != SCTP_XMIT_OK) { if (status != SCTP_XMIT_OK) {
/* We could not append this chunk, so put /* We could not append this chunk, so put
* the chunk back on the output queue. * the chunk back on the output queue.
@ -1138,7 +1116,7 @@ static void sctp_outq_flush_data(struct sctp_outq *q,
__func__, ntohl(chunk->subh.data_hdr->tsn), __func__, ntohl(chunk->subh.data_hdr->tsn),
status); status);
sctp_outq_head_data(q, chunk); sctp_outq_head_data(ctx->q, chunk);
break; break;
} }
@ -1146,48 +1124,46 @@ static void sctp_outq_flush_data(struct sctp_outq *q,
* The sender MAY set the I-bit in the DATA * The sender MAY set the I-bit in the DATA
* chunk header. * chunk header.
*/ */
if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING) if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM; chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED) if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
asoc->stats.ouodchunks++; ctx->asoc->stats.ouodchunks++;
else else
asoc->stats.oodchunks++; ctx->asoc->stats.oodchunks++;
/* Only now it's safe to consider this /* Only now it's safe to consider this
* chunk as sent, sched-wise. * chunk as sent, sched-wise.
*/ */
sctp_sched_dequeue_done(q, chunk); sctp_sched_dequeue_done(ctx->q, chunk);
list_add_tail(&chunk->transmitted_list, list_add_tail(&chunk->transmitted_list,
&transport->transmitted); &ctx->transport->transmitted);
sctp_transport_reset_t3_rtx(transport); sctp_transport_reset_t3_rtx(ctx->transport);
transport->last_time_sent = jiffies; ctx->transport->last_time_sent = jiffies;
/* Only let one DATA chunk get bundled with a /* Only let one DATA chunk get bundled with a
* COOKIE-ECHO chunk. * COOKIE-ECHO chunk.
*/ */
if (packet->has_cookie_echo) if (ctx->packet->has_cookie_echo)
break; break;
} }
} }
static void sctp_outq_flush_transports(struct sctp_outq *q, static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
struct list_head *transport_list,
gfp_t gfp)
{ {
struct list_head *ltransport; struct list_head *ltransport;
struct sctp_packet *packet; struct sctp_packet *packet;
struct sctp_transport *t; struct sctp_transport *t;
int error = 0; int error = 0;
while ((ltransport = sctp_list_dequeue(transport_list)) != NULL) { while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) {
t = list_entry(ltransport, struct sctp_transport, send_ready); t = list_entry(ltransport, struct sctp_transport, send_ready);
packet = &t->packet; packet = &t->packet;
if (!sctp_packet_empty(packet)) { if (!sctp_packet_empty(packet)) {
error = sctp_packet_transmit(packet, gfp); error = sctp_packet_transmit(packet, ctx->gfp);
if (error < 0) if (error < 0)
q->asoc->base.sk->sk_err = -error; ctx->q->asoc->base.sk->sk_err = -error;
} }
/* Clear the burst limited state, if any */ /* Clear the burst limited state, if any */
@ -1195,8 +1171,7 @@ static void sctp_outq_flush_transports(struct sctp_outq *q,
} }
} }
/* /* Try to flush an outqueue.
* Try to flush an outqueue.
* *
* Description: Send everything in q which we legally can, subject to * Description: Send everything in q which we legally can, subject to
* congestion limitations. * congestion limitations.
@ -1204,15 +1179,19 @@ static void sctp_outq_flush_transports(struct sctp_outq *q,
* locking concerns must be made. Today we use the sock lock to protect * locking concerns must be made. Today we use the sock lock to protect
* this function. * this function.
*/ */
static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp) static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
{ {
/* Current transport being used. It's NOT the same as curr active one */ struct sctp_flush_ctx ctx = {
struct sctp_transport *transport = NULL; .q = q,
/* These transports have chunks to send. */ .transport = NULL,
LIST_HEAD(transport_list); .transport_list = LIST_HEAD_INIT(ctx.transport_list),
.asoc = q->asoc,
.packet = NULL,
.gfp = gfp,
};
/* /* 6.10 Bundling
* 6.10 Bundling
* ... * ...
* When bundling control chunks with DATA chunks, an * When bundling control chunks with DATA chunks, an
* endpoint MUST place control chunks first in the outbound * endpoint MUST place control chunks first in the outbound
@ -1221,16 +1200,16 @@ static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
* ... * ...
*/ */
sctp_outq_flush_ctrl(q, &transport, &transport_list, gfp); sctp_outq_flush_ctrl(&ctx);
if (q->asoc->src_out_of_asoc_ok) if (q->asoc->src_out_of_asoc_ok)
goto sctp_flush_out; goto sctp_flush_out;
sctp_outq_flush_data(q, &transport, &transport_list, rtx_timeout, gfp); sctp_outq_flush_data(&ctx, rtx_timeout);
sctp_flush_out: sctp_flush_out:
sctp_outq_flush_transports(q, &transport_list, gfp); sctp_outq_flush_transports(&ctx);
} }
/* Update unack_data based on the incoming SACK chunk */ /* Update unack_data based on the incoming SACK chunk */
@ -1783,7 +1762,7 @@ static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
if (TSN_lte(tsn, ctsn)) if (TSN_lte(tsn, ctsn))
goto pass; goto pass;
/* 3.3.4 Selective Acknowledgement (SACK) (3): /* 3.3.4 Selective Acknowledgment (SACK) (3):
* *
* Gap Ack Blocks: * Gap Ack Blocks:
* These fields contain the Gap Ack Blocks. They are repeated * These fields contain the Gap Ack Blocks. They are repeated