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-rw-r--r--net/ipv4/tcp_input.c86
1 files changed, 44 insertions, 42 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 2877c3e..53c8ce40 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -105,7 +105,6 @@ int sysctl_tcp_abc __read_mostly;
#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
#define FLAG_DATA_SACKED 0x20 /* New SACK. */
#define FLAG_ECE 0x40 /* ECE in this ACK */
-#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
#define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
@@ -1040,13 +1039,11 @@ static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp,
* These 6 states form finite state machine, controlled by the following events:
* 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
* 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
- * 3. Loss detection event of one of three flavors:
+ * 3. Loss detection event of two flavors:
* A. Scoreboard estimator decided the packet is lost.
* A'. Reno "three dupacks" marks head of queue lost.
- * A''. Its FACK modfication, head until snd.fack is lost.
- * B. SACK arrives sacking data transmitted after never retransmitted
- * hole was sent out.
- * C. SACK arrives sacking SND.NXT at the moment, when the
+ * A''. Its FACK modification, head until snd.fack is lost.
+ * B. SACK arrives sacking SND.NXT at the moment, when the
* segment was retransmitted.
* 4. D-SACK added new rule: D-SACK changes any tag to S.
*
@@ -1153,7 +1150,7 @@ static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack,
}
/* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
- * Event "C". Later note: FACK people cheated me again 8), we have to account
+ * Event "B". Later note: FACK people cheated me again 8), we have to account
* for reordering! Ugly, but should help.
*
* Search retransmitted skbs from write_queue that were sent when snd_nxt was
@@ -1310,25 +1307,26 @@ static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
return in_sack;
}
-static u8 tcp_sacktag_one(const struct sk_buff *skb, struct sock *sk,
- struct tcp_sacktag_state *state,
+/* Mark the given newly-SACKed range as such, adjusting counters and hints. */
+static u8 tcp_sacktag_one(struct sock *sk,
+ struct tcp_sacktag_state *state, u8 sacked,
+ u32 start_seq, u32 end_seq,
int dup_sack, int pcount)
{
struct tcp_sock *tp = tcp_sk(sk);
- u8 sacked = TCP_SKB_CB(skb)->sacked;
int fack_count = state->fack_count;
/* Account D-SACK for retransmitted packet. */
if (dup_sack && (sacked & TCPCB_RETRANS)) {
if (tp->undo_marker && tp->undo_retrans &&
- after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
+ after(end_seq, tp->undo_marker))
tp->undo_retrans--;
if (sacked & TCPCB_SACKED_ACKED)
state->reord = min(fack_count, state->reord);
}
/* Nothing to do; acked frame is about to be dropped (was ACKed). */
- if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
+ if (!after(end_seq, tp->snd_una))
return sacked;
if (!(sacked & TCPCB_SACKED_ACKED)) {
@@ -1347,13 +1345,13 @@ static u8 tcp_sacktag_one(const struct sk_buff *skb, struct sock *sk,
/* New sack for not retransmitted frame,
* which was in hole. It is reordering.
*/
- if (before(TCP_SKB_CB(skb)->seq,
+ if (before(start_seq,
tcp_highest_sack_seq(tp)))
state->reord = min(fack_count,
state->reord);
/* SACK enhanced F-RTO (RFC4138; Appendix B) */
- if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
+ if (!after(end_seq, tp->frto_highmark))
state->flag |= FLAG_ONLY_ORIG_SACKED;
}
@@ -1371,8 +1369,7 @@ static u8 tcp_sacktag_one(const struct sk_buff *skb, struct sock *sk,
/* 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))
+ before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq))
tp->lost_cnt_hint += pcount;
if (fack_count > tp->fackets_out)
@@ -1391,6 +1388,9 @@ static u8 tcp_sacktag_one(const struct sk_buff *skb, struct sock *sk,
return sacked;
}
+/* Shift newly-SACKed bytes from this skb to the immediately previous
+ * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
+ */
static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
struct tcp_sacktag_state *state,
unsigned int pcount, int shifted, int mss,
@@ -1398,10 +1398,13 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
{
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *prev = tcp_write_queue_prev(sk, skb);
+ u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */
+ u32 end_seq = start_seq + shifted; /* end of newly-SACKed */
BUG_ON(!pcount);
- if (skb == tp->lost_skb_hint)
+ /* Adjust hint for FACK. Non-FACK is handled in tcp_sacktag_one(). */
+ if (tcp_is_fack(tp) && (skb == tp->lost_skb_hint))
tp->lost_cnt_hint += pcount;
TCP_SKB_CB(prev)->end_seq += shifted;
@@ -1427,8 +1430,11 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
skb_shinfo(skb)->gso_type = 0;
}
- /* We discard results */
- tcp_sacktag_one(skb, sk, state, dup_sack, pcount);
+ /* Adjust counters and hints for the newly sacked sequence range but
+ * discard the return value since prev is already marked.
+ */
+ tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked,
+ start_seq, end_seq, dup_sack, pcount);
/* Difference in this won't matter, both ACKed by the same cumul. ACK */
TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
@@ -1667,10 +1673,14 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
break;
if (in_sack) {
- TCP_SKB_CB(skb)->sacked = tcp_sacktag_one(skb, sk,
- state,
- dup_sack,
- tcp_skb_pcount(skb));
+ TCP_SKB_CB(skb)->sacked =
+ tcp_sacktag_one(sk,
+ state,
+ TCP_SKB_CB(skb)->sacked,
+ TCP_SKB_CB(skb)->seq,
+ TCP_SKB_CB(skb)->end_seq,
+ dup_sack,
+ tcp_skb_pcount(skb));
if (!before(TCP_SKB_CB(skb)->seq,
tcp_highest_sack_seq(tp)))
@@ -1844,10 +1854,6 @@ tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb,
if (found_dup_sack && ((i + 1) == first_sack_index))
next_dup = &sp[i + 1];
- /* Event "B" in the comment above. */
- if (after(end_seq, tp->high_seq))
- state.flag |= FLAG_DATA_LOST;
-
/* Skip too early cached blocks */
while (tcp_sack_cache_ok(tp, cache) &&
!before(start_seq, cache->end_seq))
@@ -2515,8 +2521,11 @@ static void tcp_timeout_skbs(struct sock *sk)
tcp_verify_left_out(tp);
}
-/* Mark head of queue up as lost. With RFC3517 SACK, the packets is
- * is against sacked "cnt", otherwise it's against facked "cnt"
+/* Detect loss in event "A" above by marking head of queue up as lost.
+ * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
+ * are considered lost. For RFC3517 SACK, a segment is considered lost if it
+ * has at least tp->reordering SACKed seqments above it; "packets" refers to
+ * the maximum SACKed segments to pass before reaching this limit.
*/
static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
{
@@ -2525,6 +2534,8 @@ static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
int cnt, oldcnt;
int err;
unsigned int mss;
+ /* Use SACK to deduce losses of new sequences sent during recovery */
+ const u32 loss_high = tcp_is_sack(tp) ? tp->snd_nxt : tp->high_seq;
WARN_ON(packets > tp->packets_out);
if (tp->lost_skb_hint) {
@@ -2546,7 +2557,7 @@ static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
tp->lost_skb_hint = skb;
tp->lost_cnt_hint = cnt;
- if (after(TCP_SKB_CB(skb)->end_seq, tp->high_seq))
+ if (after(TCP_SKB_CB(skb)->end_seq, loss_high))
break;
oldcnt = cnt;
@@ -3033,19 +3044,10 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
if (tcp_check_sack_reneging(sk, flag))
return;
- /* C. Process data loss notification, provided it is valid. */
- if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) &&
- before(tp->snd_una, tp->high_seq) &&
- icsk->icsk_ca_state != TCP_CA_Open &&
- tp->fackets_out > tp->reordering) {
- tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering, 0);
- NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSS);
- }
-
- /* D. Check consistency of the current state. */
+ /* C. Check consistency of the current state. */
tcp_verify_left_out(tp);
- /* E. Check state exit conditions. State can be terminated
+ /* D. Check state exit conditions. State can be terminated
* when high_seq is ACKed. */
if (icsk->icsk_ca_state == TCP_CA_Open) {
WARN_ON(tp->retrans_out != 0);
@@ -3077,7 +3079,7 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
}
}
- /* F. Process state. */
+ /* E. Process state. */
switch (icsk->icsk_ca_state) {
case TCP_CA_Recovery:
if (!(flag & FLAG_SND_UNA_ADVANCED)) {
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