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authorJesper Dangaard Brouer <brouer@redhat.com>2022-07-11 17:04:22 +0300
committerAndrii Nakryiko <andrii@kernel.org>2022-07-12 07:14:35 +0300
commit49705c4ab324654a7038fc843255140730477e04 (patch)
tree641956d6ecc8a0854cf899c798af9523153200fc
parentefc9909fdce00a827a37609628223cd45bf95d0b (diff)
downloadlinux-49705c4ab324654a7038fc843255140730477e04.tar.xz
samples/bpf: Fix xdp_redirect_map egress devmap prog
LLVM compiler optimized out the memcpy in xdp_redirect_map_egress, which caused the Ethernet source MAC-addr to always be zero when enabling the devmap egress prog via cmdline --load-egress. Issue observed with LLVM version 14.0.0 - Shipped with Fedora 36 on target: x86_64-redhat-linux-gnu. In verbose mode print the source MAC-addr in case xdp_devmap_attached mode is used. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/165754826292.575614.5636444052787717159.stgit@firesoul
-rw-r--r--samples/bpf/xdp_redirect_map.bpf.c6
-rw-r--r--samples/bpf/xdp_redirect_map_user.c9
2 files changed, 13 insertions, 2 deletions
diff --git a/samples/bpf/xdp_redirect_map.bpf.c b/samples/bpf/xdp_redirect_map.bpf.c
index 415bac1758e3..8557c278df77 100644
--- a/samples/bpf/xdp_redirect_map.bpf.c
+++ b/samples/bpf/xdp_redirect_map.bpf.c
@@ -33,7 +33,7 @@ struct {
} tx_port_native SEC(".maps");
/* store egress interface mac address */
-const volatile char tx_mac_addr[ETH_ALEN];
+const volatile __u8 tx_mac_addr[ETH_ALEN];
static __always_inline int xdp_redirect_map(struct xdp_md *ctx, void *redirect_map)
{
@@ -73,6 +73,7 @@ int xdp_redirect_map_egress(struct xdp_md *ctx)
{
void *data_end = (void *)(long)ctx->data_end;
void *data = (void *)(long)ctx->data;
+ u8 *mac_addr = (u8 *) tx_mac_addr;
struct ethhdr *eth = data;
u64 nh_off;
@@ -80,7 +81,8 @@ int xdp_redirect_map_egress(struct xdp_md *ctx)
if (data + nh_off > data_end)
return XDP_DROP;
- __builtin_memcpy(eth->h_source, (const char *)tx_mac_addr, ETH_ALEN);
+ barrier_var(mac_addr); /* prevent optimizing out memcpy */
+ __builtin_memcpy(eth->h_source, mac_addr, ETH_ALEN);
return XDP_PASS;
}
diff --git a/samples/bpf/xdp_redirect_map_user.c b/samples/bpf/xdp_redirect_map_user.c
index b6e4fc849577..c889a1394dc1 100644
--- a/samples/bpf/xdp_redirect_map_user.c
+++ b/samples/bpf/xdp_redirect_map_user.c
@@ -40,6 +40,8 @@ static const struct option long_options[] = {
{}
};
+static int verbose = 0;
+
int main(int argc, char **argv)
{
struct bpf_devmap_val devmap_val = {};
@@ -79,6 +81,7 @@ int main(int argc, char **argv)
break;
case 'v':
sample_switch_mode();
+ verbose = 1;
break;
case 's':
mask |= SAMPLE_REDIRECT_MAP_CNT;
@@ -134,6 +137,12 @@ int main(int argc, char **argv)
ret = EXIT_FAIL;
goto end_destroy;
}
+ if (verbose)
+ printf("Egress ifindex:%d using src MAC %02x:%02x:%02x:%02x:%02x:%02x\n",
+ ifindex_out,
+ skel->rodata->tx_mac_addr[0], skel->rodata->tx_mac_addr[1],
+ skel->rodata->tx_mac_addr[2], skel->rodata->tx_mac_addr[3],
+ skel->rodata->tx_mac_addr[4], skel->rodata->tx_mac_addr[5]);
}
skel->rodata->from_match[0] = ifindex_in;