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pping: Keep track of outstanding timestamps

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Add a counter of outstanding (unmatched) timestamped entires in the
flow state. Before a timestamp lookup is attempted, check that there
are any outstanding timestamps, otherwise avoid the unecessary hash
map lookup.

Use 32 bit counter for outstanding timestamps to allow atomic
increments/decrements using __synch_fetch_and_add. This operation is
not supported on smaller integers, which is why such a large counter
is used. The atomicity is needed because the counter may be
concurrently accessed by both the ingress/egress hook as well as the
periodical map cleanup.

Signed-off-by: Simon Sundberg <simon.sundberg@kau.se>
This commit is contained in:
Simon Sundberg
2022-03-09 22:19:59 +01:00
parent a6e4dd8748
commit 11f1d88742
2 changed files with 17 additions and 4 deletions
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3
pping/pping.h
View File

@@ -94,9 +94,10 @@ struct flow_state {
__u64 rec_pkts;
__u64 rec_bytes;
__u32 last_id;
__u32 outstanding_timestamps;
bool has_opened;
enum flow_event_reason opening_reason;
__u16 reserved;
__u8 reserved[6];
};
struct packet_id {

18
pping/pping_kern.c
View File

@@ -687,7 +687,9 @@ static void pping_timestamp_packet(struct flow_state *f_state, void *ctx,
f_state->last_timestamp = p_info->time;
if (bpf_map_update_elem(&packet_ts, &p_info->pid, &p_info->time,
BPF_NOEXIST) != 0)
BPF_NOEXIST) == 0)
__sync_fetch_and_add(&f_state->outstanding_timestamps, 1);
else
send_map_full_event(ctx, p_info, PPING_MAP_PACKETTS);
}
@@ -704,6 +706,9 @@ static void pping_match_packet(struct flow_state *f_state, void *ctx,
if (!f_state || !p_info->reply_pid_valid)
return;
if (f_state->outstanding_timestamps == 0)
return;
p_ts = bpf_map_lookup_elem(&packet_ts, &p_info->reply_pid);
if (!p_ts || p_info->time < *p_ts)
return;
@@ -711,8 +716,10 @@ static void pping_match_packet(struct flow_state *f_state, void *ctx,
re.rtt = p_info->time - *p_ts;
// Delete timestamp entry as soon as RTT is calculated
if (bpf_map_delete_elem(&packet_ts, &p_info->reply_pid) == 0)
if (bpf_map_delete_elem(&packet_ts, &p_info->reply_pid) == 0) {
__sync_fetch_and_add(&f_state->outstanding_timestamps, -1);
debug_increment_autodel(PPING_MAP_PACKETTS);
}
if (f_state->min_rtt == 0 || re.rtt < f_state->min_rtt)
f_state->min_rtt = re.rtt;
@@ -836,8 +843,13 @@ int tsmap_cleanup(struct bpf_iter__bpf_map_elem *ctx)
if ((rtt && now - *timestamp > rtt * TIMESTAMP_RTT_LIFETIME) ||
now - *timestamp > TIMESTAMP_LIFETIME) {
if (bpf_map_delete_elem(&packet_ts, &local_pid) == 0)
if (bpf_map_delete_elem(&packet_ts, &local_pid) == 0) {
debug_increment_timeoutdel(PPING_MAP_PACKETTS);
if (f_state)
__sync_fetch_and_add(
&f_state->outstanding_timestamps, -1);
}
}
return 0;