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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>
This commit is contained in:
Jesper Dangaard Brouer 2017-08-17 18:22:37 +02:00 committed by David S. Miller
parent d2cee2e5d0
commit 4c03bdd7b5
2 changed files with 19 additions and 11 deletions
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11
include/trace/events/xdp.h
View File

@ -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 */

19
net/core/filter.c
View File

@ -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);