On Wed, Apr 24, 2024 at 03:50:51PM +0200, Adrian Moreno wrote:
Currently there are no widely-available tools to dump the metadata and
group information when a packet is sampled, making it difficult to
troubleshoot related issues.
This makes psample use the event tracing framework to log the sampling
of a packet so that it's easier to quickly identify the source
(i.e: group) and context (i.e: metadata) of a packet being sampled.
This patch creates some checkpatch splats, but the style of the
tracepoint definition mimics that of other modules so it seems
acceptable.
I don't see a good reason to add this tracepoint (which we won't be able
to remove) when you can easily do that with bpftrace which by now should
be widely available:
#!/usr/bin/bpftrace
kfunc:psample_sample_packet
{
$ts_us = nsecs() / 1000;
$secs = $ts_us / 1000000;
$us = $ts_us % 1000000;
$group = args.group;
$skb = args.skb;
$md = args.md;
printf("%-16s %-6d %6llu.%6llu group_num = %u refcount=%u seq=%u skbaddr=%p len=%u data_len=%u sample_rate=%u in_ifindex=%d out_ifindex=%d user_cookie=%rx\n",
comm, pid, $secs, $us, $group->group_num, $group->refcount, $group->seq,
$skb, $skb->len, $skb->data_len, args.sample_rate,
$md->in_ifindex, $md->out_ifindex,
buf($md->user_cookie, $md->user_cookie_len));
}
Example output:
mausezahn 984 3299.200626 group_num = 1 refcount=1 seq=13775 skbaddr=0xffffa21143fd4000 len=42 data_len=0 sample_rate=10 in_ifindex=0 out_ifindex=20 user_cookie=
\xde\xad\xbe\xef
mausezahn 984 3299.281424 group_num = 1 refcount=1 seq=13776 skbaddr=0xffffa21143fd4000 len=42 data_len=0 sample_rate=10 in_ifindex=0 out_ifindex=20 user_cookie=
\xde\xad\xbe\xef
Note that it prints the cookie itself unlike the tracepoint which only
prints the hashed pointer.
Signed-off-by: Adrian Moreno <amorenoz@xxxxxxxxxx>
---
net/psample/psample.c | 9 +++++++
net/psample/trace.h | 62 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 71 insertions(+)
create mode 100644 net/psample/trace.h
diff --git a/net/psample/psample.c b/net/psample/psample.c
index 476aaad7a885..92db8ffa2ba2 100644
--- a/net/psample/psample.c
+++ b/net/psample/psample.c
@@ -18,6 +18,12 @@
#include <net/ip_tunnels.h>
#include <net/dst_metadata.h>
+#ifndef __CHECKER__
+#define CREATE_TRACE_POINTS
+#endif
+
+#include "trace.h"
+
#define PSAMPLE_MAX_PACKET_SIZE 0xffff
static LIST_HEAD(psample_groups_list);
@@ -470,6 +476,9 @@ void psample_sample_packet(struct psample_group *group, struct sk_buff *skb,
void *data;
int ret;
+ if (trace_psample_sample_packet_enabled())
+ trace_psample_sample_packet(group, skb, sample_rate, md);
My understanding is that trace_x_enabled() should only be used if you
need to do some work to prepare parameters for the tracepoint.
+
meta_len = (in_ifindex ? nla_total_size(sizeof(u16)) : 0) +
(out_ifindex ? nla_total_size(sizeof(u16)) : 0) +
(md->out_tc_valid ? nla_total_size(sizeof(u16)) : 0) +