Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Thu, 25 Apr 2024 10:18:22 +0300 | From | Ido Schimmel <> | Subject | Re: [PATCH net-next 4/8] net: psample: add tracepoint |
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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@redhat.com> > --- > 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) +
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