netdev - [PATCH net-next 2/7] xdp: tracepoint xdp_redirect also need a map argument

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Date:   Tue, 29 Aug 2017 16:37:45 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     netdev@...r.kernel.org
Cc:     John Fastabend <john.fastabend@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Subject: [PATCH net-next 2/7] xdp: tracepoint xdp_redirect also need a map
 argument

To make sense of the map index, the tracepoint user also need to know
that map we are talking about.  Supply the map pointer but only expose
the map->id.

The 'to_index' is renamed 'to_ifindex'.  In the xdp_redirect_map case,
this is the result of the devmap lookup. The map lookup key is exposed
as map_index, which is needed to troubleshoot in case the lookup failed.
The 'to_ifindex' is placed after 'err' to keep TP_STRUCT as common as
possible.

This also keeps the TP_STRUCT similar enough, that userspace can write
a monitor program, that doesn't need to care about whether
bpf_redirect or bpf_redirect_map were used.

Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
---
 include/trace/events/xdp.h |   38 ++++++++++++++++++++++++++++++--------
 net/core/filter.c          |    6 +++---
 2 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index f684f3b36bca..573dcfa1aeaa 100644
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -49,20 +49,23 @@ TRACE_EVENT(xdp_exception,
 		  __entry->ifindex)
 );
 
-TRACE_EVENT(xdp_redirect,
+DECLARE_EVENT_CLASS(xdp_redirect_template,
 
 	TP_PROTO(const struct net_device *dev,
 		 const struct bpf_prog *xdp,
-		 int to_index, int err),
+		 int to_ifindex, int err,
+		 const struct bpf_map *map, u32 map_index),
 
-	TP_ARGS(dev, xdp, to_index, err),
+	TP_ARGS(dev, xdp, to_ifindex, err, map, map_index),
 
 	TP_STRUCT__entry(
 		__array(u8, prog_tag, 8)
 		__field(u32, act)
 		__field(int, ifindex)
-		__field(int, to_index)
 		__field(int, err)
+		__field(int, to_ifindex)
+		__field(u32, map_id)
+		__field(int, map_index)
 	),
 
 	TP_fast_assign(
@@ -70,16 +73,35 @@ TRACE_EVENT(xdp_redirect,
 		memcpy(__entry->prog_tag, xdp->tag, sizeof(xdp->tag));
 		__entry->act		= XDP_REDIRECT;
 		__entry->ifindex	= dev->ifindex;
-		__entry->to_index	= to_index;
 		__entry->err		= err;
+		__entry->to_ifindex	= to_ifindex;
+		__entry->map_id		= map ? map->id : 0;
+		__entry->map_index	= map_index;
 	),
 
-	TP_printk("prog=%s action=%s ifindex=%d to_index=%d err=%d",
+	TP_printk("prog=%s action=%s ifindex=%d to_ifindex=%d err=%d"
+		  " map_id=%d map_index=%d",
 		  __print_hex_str(__entry->prog_tag, 8),
 		  __print_symbolic(__entry->act, __XDP_ACT_SYM_TAB),
-		  __entry->ifindex, __entry->to_index,
-		  __entry->err)
+		  __entry->ifindex, __entry->to_ifindex,
+		  __entry->err,
+		  __entry->map_id, __entry->map_index)
 );
+
+DEFINE_EVENT(xdp_redirect_template, xdp_redirect,
+	TP_PROTO(const struct net_device *dev,
+		 const struct bpf_prog *xdp,
+		 int to_ifindex, int err,
+		 const struct bpf_map *map, u32 map_index),
+	TP_ARGS(dev, xdp, to_ifindex, err, map, map_index)
+);
+
+#define _trace_xdp_redirect(dev, xdp, to, err)	\
+	 trace_xdp_redirect(dev, xdp, to, err, NULL, 0);
+
+#define trace_xdp_redirect_map(dev, xdp, fwd, err, map, idx)	\
+	trace_xdp_redirect(dev, xdp, fwd ? fwd->ifindex : 0, err, map, idx);
+
 #endif /* _TRACE_XDP_H */
 
 #include <trace/define_trace.h>
diff --git a/net/core/filter.c b/net/core/filter.c
index de31fb684ad4..31eab77cc842 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2524,7 +2524,7 @@ static int xdp_do_redirect_map(struct net_device *dev, struct xdp_buff *xdp,
 	if (likely(!err))
 		ri->map_to_flush = map;
 out:
-	trace_xdp_redirect(dev, xdp_prog, index, err);
+	trace_xdp_redirect_map(dev, xdp_prog, fwd, err, map, index);
 	return err;
 }
 
@@ -2548,7 +2548,7 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
 
 	err = __bpf_tx_xdp(fwd, NULL, xdp, 0);
 out:
-	trace_xdp_redirect(dev, xdp_prog, index, err);
+	_trace_xdp_redirect(dev, xdp_prog, index, err);
 	return err;
 }
 EXPORT_SYMBOL_GPL(xdp_do_redirect);
@@ -2582,7 +2582,7 @@ int xdp_do_generic_redirect(struct net_device *dev, struct sk_buff *skb,
 
 	skb->dev = fwd;
 out:
-	trace_xdp_redirect(dev, xdp_prog, index, err);
+	_trace_xdp_redirect(dev, xdp_prog, index, err);
 	return err;
 }
 EXPORT_SYMBOL_GPL(xdp_do_generic_redirect);