xdp: adjust xdp redirect tracepoint to include return error code

The return error code need to be included in the tracepoint
xdp:xdp_redirect, else its not possible to distinguish successful or
failed XDP_REDIRECT transmits.

XDP have no queuing mechanism. Thus, it is fairly easily to overrun a
NIC transmit queue.  The eBPF program invoking helpers (bpf_redirect
or bpf_redirect_map) to redirect a packet doesn't get any feedback
whether the packet was actually transmitted.

Info on failed transmits in the tracepoint xdp:xdp_redirect, is
interesting as this opens for providing a feedback-loop to the
receiving XDP program.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index 7b1eb7b..0e42e69 100644 (file)
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -53,15 +53,16 @@ TRACE_EVENT(xdp_redirect,
 
        TP_PROTO(const struct net_device *from,
                 const struct net_device *to,
-                const struct bpf_prog *xdp, u32 act),
+                const struct bpf_prog *xdp, u32 act, int err),
 
-       TP_ARGS(from, to, xdp, act),
+       TP_ARGS(from, to, xdp, act, err),
 
        TP_STRUCT__entry(
                __string(name_from, from->name)
                __string(name_to, to->name)
                __array(u8, prog_tag, 8)
                __field(u32, act)
+               __field(int, err)
        ),
 
        TP_fast_assign(
@@ -70,12 +71,14 @@ TRACE_EVENT(xdp_redirect,
                __assign_str(name_from, from->name);
                __assign_str(name_to, to->name);
                __entry->act = act;
+               __entry->err = err;
        ),
 
-       TP_printk("prog=%s from=%s to=%s action=%s",
+       TP_printk("prog=%s from=%s to=%s action=%s 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))
+                 __print_symbolic(__entry->act, __XDP_ACT_SYM_TAB),
+                 __entry->err)
 );
 #endif /* _TRACE_XDP_H */
 

diff --git a/net/core/filter.c b/net/core/filter.c
index 0f4df86..fa21156 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2535,14 +2535,16 @@ int xdp_do_redirect_map(struct net_device *dev, struct xdp_buff *xdp,
        struct bpf_map *map = ri->map;
        u32 index = ri->ifindex;
        struct net_device *fwd;
-       int err = -EINVAL;
+       int err;
 
        ri->ifindex = 0;
        ri->map = NULL;
 
        fwd = __dev_map_lookup_elem(map, index);
-       if (!fwd)
+       if (!fwd) {
+               err = -EINVAL;
                goto out;
+       }
 
        if (ri->map_to_flush && (ri->map_to_flush != map))
                xdp_do_flush_map();
@@ -2552,7 +2554,7 @@ 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);
+       trace_xdp_redirect(dev, fwd, xdp_prog, XDP_REDIRECT, err);
        return err;
 }
 
@@ -2562,6 +2564,7 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
        struct redirect_info *ri = this_cpu_ptr(&redirect_info);
        struct net_device *fwd;
        u32 index = ri->ifindex;
+       int err;
 
        if (ri->map)
                return xdp_do_redirect_map(dev, xdp, xdp_prog);
@@ -2570,12 +2573,14 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
        ri->ifindex = 0;
        if (unlikely(!fwd)) {
                bpf_warn_invalid_xdp_redirect(index);
-               return -EINVAL;
+               err = -EINVAL;
+               goto out;
        }
 
-       trace_xdp_redirect(dev, fwd, xdp_prog, XDP_REDIRECT);
-
-       return __bpf_tx_xdp(fwd, NULL, xdp, 0);
+       err = __bpf_tx_xdp(fwd, NULL, xdp, 0);
+out:
+       trace_xdp_redirect(dev, fwd, xdp_prog, XDP_REDIRECT, err);
+       return err;
 }
 EXPORT_SYMBOL_GPL(xdp_do_redirect);