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3fd9dcd689
The AF_XDP userspace part of xdp_hw_metadata see non-zero as a signal of
the availability of rx_timestamp and rx_hash in data_meta area. The
kernel-side BPF-prog code doesn't initialize these members when kernel
returns an error e.g. -EOPNOTSUPP. This memory area is not guaranteed to
be zeroed, and can contain garbage/previous values, which will be read
and interpreted by AF_XDP userspace side.
Tested this on different drivers. The experiences are that for most
packets they will have zeroed this data_meta area, but occasionally it
will contain garbage data.
Example of failure tested on ixgbe:
poll: 1 (0)
xsk_ring_cons__peek: 1
0x18ec788: rx_desc[0]->addr=100000000008000 addr=8100 comp_addr=8000
rx_hash: 3697961069
rx_timestamp: 9024981991734834796 (sec:9024981991.7348)
0x18ec788: complete idx=8 addr=8000
Converting to date:
date -d @9024981991
2255-12-28T20:26:31 CET
I choose a simple fix in this patch. When kfunc fails or isn't supported
assign zero to the corresponding struct meta value.
It's up to the individual BPF-programmer to do something smarter e.g.
that fits their use-case, like getting a software timestamp and marking
a flag that gives the type of timestamp.
Fixes: 297a3f1241 ("selftests/bpf: Simple program to dump XDP RX metadata")
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/167527271027.937063.5177725618616476592.stgit@firesoul
86 lines
2.1 KiB
C
86 lines
2.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <vmlinux.h>
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#include "xdp_metadata.h"
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_endian.h>
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struct {
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__uint(type, BPF_MAP_TYPE_XSKMAP);
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__uint(max_entries, 256);
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__type(key, __u32);
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__type(value, __u32);
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} xsk SEC(".maps");
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extern int bpf_xdp_metadata_rx_timestamp(const struct xdp_md *ctx,
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__u64 *timestamp) __ksym;
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extern int bpf_xdp_metadata_rx_hash(const struct xdp_md *ctx,
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__u32 *hash) __ksym;
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SEC("xdp")
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int rx(struct xdp_md *ctx)
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{
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void *data, *data_meta, *data_end;
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struct ipv6hdr *ip6h = NULL;
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struct ethhdr *eth = NULL;
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struct udphdr *udp = NULL;
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struct iphdr *iph = NULL;
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struct xdp_meta *meta;
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int ret;
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data = (void *)(long)ctx->data;
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data_end = (void *)(long)ctx->data_end;
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eth = data;
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if (eth + 1 < data_end) {
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if (eth->h_proto == bpf_htons(ETH_P_IP)) {
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iph = (void *)(eth + 1);
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if (iph + 1 < data_end && iph->protocol == IPPROTO_UDP)
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udp = (void *)(iph + 1);
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}
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if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
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ip6h = (void *)(eth + 1);
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if (ip6h + 1 < data_end && ip6h->nexthdr == IPPROTO_UDP)
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udp = (void *)(ip6h + 1);
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}
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if (udp && udp + 1 > data_end)
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udp = NULL;
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}
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if (!udp)
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return XDP_PASS;
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if (udp->dest != bpf_htons(9091))
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return XDP_PASS;
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bpf_printk("forwarding UDP:9091 to AF_XDP");
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ret = bpf_xdp_adjust_meta(ctx, -(int)sizeof(struct xdp_meta));
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if (ret != 0) {
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bpf_printk("bpf_xdp_adjust_meta returned %d", ret);
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return XDP_PASS;
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}
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data = (void *)(long)ctx->data;
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data_meta = (void *)(long)ctx->data_meta;
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meta = data_meta;
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if (meta + 1 > data) {
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bpf_printk("bpf_xdp_adjust_meta doesn't appear to work");
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return XDP_PASS;
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}
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if (!bpf_xdp_metadata_rx_timestamp(ctx, &meta->rx_timestamp))
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bpf_printk("populated rx_timestamp with %llu", meta->rx_timestamp);
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else
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meta->rx_timestamp = 0; /* Used by AF_XDP as not avail signal */
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if (!bpf_xdp_metadata_rx_hash(ctx, &meta->rx_hash))
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bpf_printk("populated rx_hash with %u", meta->rx_hash);
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else
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meta->rx_hash = 0; /* Used by AF_XDP as not avail signal */
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return bpf_redirect_map(&xsk, ctx->rx_queue_index, XDP_PASS);
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}
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char _license[] SEC("license") = "GPL";
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