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author | Jesper Dangaard Brouer <brouer@redhat.com> | 2020-05-14 12:49:33 +0200 |
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committer | Alexei Starovoitov <ast@kernel.org> | 2020-05-15 06:21:54 +0200 |
commit | 34cc0b338a61de3eee3a2bfcaf4f9d6e9fae091a (patch) | |
tree | fb51ed98a7080db136df2260b9de579b645482ef /include/net/xdp.h | |
parent | net: XDP-generic determining XDP frame size (diff) | |
download | linux-34cc0b338a61de3eee3a2bfcaf4f9d6e9fae091a.tar.xz linux-34cc0b338a61de3eee3a2bfcaf4f9d6e9fae091a.zip |
xdp: Xdp_frame add member frame_sz and handle in convert_to_xdp_frame
Use hole in struct xdp_frame, when adding member frame_sz, which keeps
same sizeof struct (32 bytes)
Drivers ixgbe and sfc had bug cases where the necessary/expected
tailroom was not reserved. This can lead to some hard to catch memory
corruption issues. Having the drivers frame_sz this can be detected when
packet length/end via xdp->data_end exceed the xdp_data_hard_end
pointer, which accounts for the reserved the tailroom.
When detecting this driver issue, simply fail the conversion with NULL,
which results in feedback to driver (failing xdp_do_redirect()) causing
driver to drop packet. Given the lack of consistent XDP stats, this can
be hard to troubleshoot. And given this is a driver bug, we want to
generate some more noise in form of a WARN stack dump (to ID the driver
code that inlined convert_to_xdp_frame).
Inlining the WARN macro is problematic, because it adds an asm
instruction (on Intel CPUs ud2) what influence instruction cache
prefetching. Thus, introduce xdp_warn and macro XDP_WARN, to avoid this
and at the same time make identifying the function and line of this
inlined function easier.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/158945337313.97035.10015729316710496600.stgit@firesoul
Diffstat (limited to 'include/net/xdp.h')
-rw-r--r-- | include/net/xdp.h | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/include/net/xdp.h b/include/net/xdp.h index a764af4ae0ea..3094fccf5a88 100644 --- a/include/net/xdp.h +++ b/include/net/xdp.h @@ -89,7 +89,8 @@ struct xdp_frame { void *data; u16 len; u16 headroom; - u16 metasize; + u32 metasize:8; + u32 frame_sz:24; /* Lifetime of xdp_rxq_info is limited to NAPI/enqueue time, * while mem info is valid on remote CPU. */ @@ -104,6 +105,10 @@ static inline void xdp_scrub_frame(struct xdp_frame *frame) frame->dev_rx = NULL; } +/* Avoids inlining WARN macro in fast-path */ +void xdp_warn(const char *msg, const char *func, const int line); +#define XDP_WARN(msg) xdp_warn(msg, __func__, __LINE__) + struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp); /* Convert xdp_buff to xdp_frame */ @@ -124,6 +129,12 @@ struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp) if (unlikely((headroom - metasize) < sizeof(*xdp_frame))) return NULL; + /* Catch if driver didn't reserve tailroom for skb_shared_info */ + if (unlikely(xdp->data_end > xdp_data_hard_end(xdp))) { + XDP_WARN("Driver BUG: missing reserved tailroom"); + return NULL; + } + /* Store info in top of packet */ xdp_frame = xdp->data_hard_start; @@ -131,6 +142,7 @@ struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp) xdp_frame->len = xdp->data_end - xdp->data; xdp_frame->headroom = headroom - sizeof(*xdp_frame); xdp_frame->metasize = metasize; + xdp_frame->frame_sz = xdp->frame_sz; /* rxq only valid until napi_schedule ends, convert to xdp_mem_info */ xdp_frame->mem = xdp->rxq->mem; |