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Subject[ 33/73] tcp: allow tcp_sacktag_one() to tag ranges not aligned with skbs
3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Neal Cardwell <ncardwell@google.com>

[ Upstream commit cc9a672ee522d4805495b98680f4a3db5d0a0af9 ]

This commit allows callers of tcp_sacktag_one() to pass in sequence
ranges that do not align with skb boundaries, as tcp_shifted_skb()
needs to do in an upcoming fix in this patch series.

In fact, now tcp_sacktag_one() does not need to depend on an input skb
at all, which makes its semantics and dependencies more clear.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/tcp_input.c | 36 ++++++++++++++++++++++--------------
1 file changed, 22 insertions(+), 14 deletions(-)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1289,25 +1289,26 @@ static int tcp_match_skb_to_sack(struct
return in_sack;
}

-static u8 tcp_sacktag_one(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)) {
@@ -1326,13 +1327,13 @@ static u8 tcp_sacktag_one(struct sk_buff
/* 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;
}

@@ -1350,8 +1351,7 @@ static u8 tcp_sacktag_one(struct sk_buff

/* 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)
@@ -1407,7 +1407,11 @@ static int tcp_shifted_skb(struct sock *
}

/* We discard results */
- tcp_sacktag_one(skb, sk, state, dup_sack, pcount);
+ tcp_sacktag_one(sk, state,
+ TCP_SKB_CB(skb)->sacked,
+ TCP_SKB_CB(skb)->seq,
+ TCP_SKB_CB(skb)->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);
@@ -1646,10 +1650,14 @@ static struct sk_buff *tcp_sacktag_walk(
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)))



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