[added missing copy to netdev@vger]
> Is this maybe necessary?
> ------------------------------>8-------------8<---------------------------------
> if packets is 0, becomes -1, but since gap is unsigned, the test 'gap > 0'
> does not work.
>
Thank you for looking through. It is not necessary, see below.
> --- a/net/dccp/ackvec.c
> +++ b/net/dccp/ackvec.c
> @@ -207,7 +207,11 @@ static inline int
> dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
> if (av->av_vec_len + packets > DCCP_MAX_ACKVEC_LEN)
> return -ENOBUFS;
>
> - gap = packets - 1;
> + if (packets > 0)
Why 'gap < 0' <=> packets < 0 can not happen:
/*
* If several packets are missing, the HC-Receiver may prefer to enter
multiple
* bytes with run length 0, rather than a single byte with a larger run
length;
* this simplifies table updates if one of the missing packets arrives.
*/
static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
const unsigned int packets,
const unsigned char state)
This is a static routine which is called in one place only in
net/dccp/ackvec.c, in dccp_ackvec_add():
//...
} else if (after48(ackno, av->av_buf_ackno)) {
const u64 delta = dccp_delta_seqno(av->av_buf_ackno, ackno);
/*
* Look if the state of this packet is the same as the
* previous ackno and if so if we can bump the head len.
*/
if (delta == 1 &&
dccp_ackvec_state(av, av->av_buf_head) == state &&
dccp_ackvec_len(av, av->av_buf_head) <
DCCP_ACKVEC_LEN_MASK)
av->av_buf[av->av_buf_head]++;
else if (dccp_ackvec_set_buf_head_state(av, delta, state))
return -ENOBUFS;
==> We thus have:
1) after48(a, b) => sequence number `a' is `after' b
2) sequence number `a' is `after' `b' => dccp_delta_seqno(b, a) > 0
3) hence delta > 0
4) hence delta - 1 = gap >= 0
5) The subsequent `else' in dccp_ackvec_add() catches the case
of !after48(a, b), note the reversed order of arguments to
dccp_delta_seqno, so that a positive value is returned:
} else {
/*
* A.1.2. Old Packets
*
* When a packet with Sequence Number S <= buf_ackno
* arrives, the HC-Receiver will scan the table for
* the byte corresponding to S. (Indexing structures
* could reduce the complexity of this scan.)
*/
u64 delta = dccp_delta_seqno(ackno, av->av_buf_ackno);
==> But this is in an entirely different block of code outside the
one to which this patch was meant.
Hence it is not necessary.
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