xdp: remove net_device names from xdp_redirect tracepoint

There is too much overhead in the current trace_xdp_redirect
tracepoint as it does strcpy and strlen on the net_device names.

Besides, exposing the ifindex/index is actually the information that
is needed in the tracepoint to diagnose issues.  When a lookup fails
(either ifindex or devmap index) then there is a need for saying which
to_index that have issues.

V2: Adjust args to be aligned with trace_xdp_exception.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/trace/events/xdp.h

@@ -51,33 +51,33 @@ TRACE_EVENT(xdp_exception,
 
 TRACE_EVENT(xdp_redirect,
 
-	TP_PROTO(const struct net_device *from,
-		 const struct net_device *to,
-		 const struct bpf_prog *xdp, u32 act, int err),
+	TP_PROTO(const struct net_device *dev,
+		 const struct bpf_prog *xdp, u32 act,
+		 int to_index, int err),
 
-	TP_ARGS(from, to, xdp, act, err),
+	TP_ARGS(dev, xdp, act, to_index, err),
 
 	TP_STRUCT__entry(
-		__string(name_from, from->name)
-		__string(name_to, to->name)
 		__array(u8, prog_tag, 8)
 		__field(u32, act)
+		__field(int, ifindex)
+		__field(int, to_index)
 		__field(int, err)
 	),
 
 	TP_fast_assign(
 		BUILD_BUG_ON(sizeof(__entry->prog_tag) != sizeof(xdp->tag));
 		memcpy(__entry->prog_tag, xdp->tag, sizeof(xdp->tag));
-		__assign_str(name_from, from->name);
-		__assign_str(name_to, to->name);
-		__entry->act = act;
-		__entry->err = err;
+		__entry->act		= act;
+		__entry->ifindex	= dev->ifindex;
+		__entry->to_index	= to_index;
+		__entry->err		= err;
 	),
 
-	TP_printk("prog=%s from=%s to=%s action=%s err=%d",
+	TP_printk("prog=%s action=%s ifindex=%d to_index=%d err=%d",
 		  __print_hex_str(__entry->prog_tag, 8),
-		  __get_str(name_from), __get_str(name_to),
 		  __print_symbolic(__entry->act, __XDP_ACT_SYM_TAB),
+		  __entry->ifindex, __entry->to_index,
 		  __entry->err)
 );
 #endif /* _TRACE_XDP_H */

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, fwd, xdp_prog, XDP_REDIRECT, err);
+	trace_xdp_redirect(dev, xdp_prog, XDP_REDIRECT, index, err);
 	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, fwd, xdp_prog, XDP_REDIRECT, err);
+	trace_xdp_redirect(dev, xdp_prog, XDP_REDIRECT, 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, fwd, xdp_prog, XDP_REDIRECT, err);
+	trace_xdp_redirect(dev, xdp_prog, XDP_REDIRECT, index, err);
 	return err;
 }
 EXPORT_SYMBOL_GPL(xdp_do_generic_redirect);