[PATCH net-next 4/5] xdp: remove net_device names from xdp_redirect tracepoint

[Jesper Dangaard Brouer]

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.

Signed-off-by: Jesper Dangaard Brouer <bro...@redhat.com>
---
 include/trace/events/xdp.h |   17 ++++++++---------
 net/core/filter.c          |    6 +++---
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index 0e42e69f773b..7511bed80558 100644
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -51,15 +51,14 @@ TRACE_EVENT(xdp_exception,
 
 TRACE_EVENT(xdp_redirect,
 
-       TP_PROTO(const struct net_device *from,
-                const struct net_device *to,
+       TP_PROTO(int from_index, int to_index,
                 const struct bpf_prog *xdp, u32 act, int err),
 
-       TP_ARGS(from, to, xdp, act, err),
+       TP_ARGS(from_index, to_index, xdp, act, err),
 
        TP_STRUCT__entry(
-               __string(name_from, from->name)
-               __string(name_to, to->name)
+               __field(int, from_index)
+               __field(int, to_index)
                __array(u8, prog_tag, 8)
                __field(u32, act)
                __field(int, err)
@@ -68,15 +67,15 @@ TRACE_EVENT(xdp_redirect,
        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->from_index     = from_index;
+               __entry->to_index       = to_index;
                __entry->act = act;
                __entry->err = err;
        ),
 
-       TP_printk("prog=%s from=%s to=%s action=%s err=%d",
+       TP_printk("prog=%s from=%d to=%d action=%s err=%d",
                  __print_hex_str(__entry->prog_tag, 8),
-                 __get_str(name_from), __get_str(name_to),
+                 __entry->from_index, __entry->to_index,
                  __print_symbolic(__entry->act, __XDP_ACT_SYM_TAB),
                  __entry->err)
 );
diff --git a/net/core/filter.c b/net/core/filter.c
index 2d7cdb2c5c66..35f0383fa2b9 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2553,7 +2553,7 @@ int xdp_do_redirect_map(struct net_device *dev, struct 
xdp_buff *xdp,
                ri->map_to_flush = map;
 
 out:
-       trace_xdp_redirect(dev, fwd, xdp_prog, XDP_REDIRECT, err);
+       trace_xdp_redirect(dev->ifindex, index, xdp_prog, XDP_REDIRECT, err);
        return err;
 }
 
@@ -2577,7 +2577,7 @@ 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->ifindex, index, xdp_prog, XDP_REDIRECT, err);
        return err;
 }
 EXPORT_SYMBOL_GPL(xdp_do_redirect);
@@ -2611,7 +2611,7 @@ 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->ifindex, index, xdp_prog, XDP_REDIRECT, err);
        return err;
 }
 EXPORT_SYMBOL_GPL(xdp_do_generic_redirect);