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Message-ID: <20250825193918.3445531-8-ameryhung@gmail.com>
Date: Mon, 25 Aug 2025 12:39:18 -0700
From: Amery Hung <ameryhung@...il.com>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org,
alexei.starovoitov@...il.com,
andrii@...nel.org,
daniel@...earbox.net,
kuba@...nel.org,
martin.lau@...nel.org,
mohsin.bashr@...il.com,
saeedm@...dia.com,
tariqt@...dia.com,
mbloch@...dia.com,
maciej.fijalkowski@...el.com,
kernel-team@...a.com
Subject: [RFC bpf-next v1 7/7] selftests: drv-net: Pull data before parsing headers
It is possible for drivers to generate xdp packets with data residing
entirely in fragments. To keep parsing headers using direcy packet
access, call bpf_xdp_pull_data() to pull headers into the linear data
area.
Signed-off-by: Amery Hung <ameryhung@...il.com>
---
.../selftests/net/lib/xdp_native.bpf.c | 90 +++++++++++++++----
1 file changed, 75 insertions(+), 15 deletions(-)
diff --git a/tools/testing/selftests/net/lib/xdp_native.bpf.c b/tools/testing/selftests/net/lib/xdp_native.bpf.c
index 521ba38f2ddd..68b2a08055ce 100644
--- a/tools/testing/selftests/net/lib/xdp_native.bpf.c
+++ b/tools/testing/selftests/net/lib/xdp_native.bpf.c
@@ -14,6 +14,9 @@
#define MAX_PAYLOAD_LEN 5000
#define MAX_HDR_LEN 64
+extern int bpf_xdp_pull_data(struct xdp_md *xdp, __u32 len,
+ __u64 flags) __ksym __weak;
+
enum {
XDP_MODE = 0,
XDP_PORT = 1,
@@ -68,30 +71,57 @@ static void record_stats(struct xdp_md *ctx, __u32 stat_type)
static struct udphdr *filter_udphdr(struct xdp_md *ctx, __u16 port)
{
- void *data_end = (void *)(long)ctx->data_end;
- void *data = (void *)(long)ctx->data;
struct udphdr *udph = NULL;
- struct ethhdr *eth = data;
+ void *data, *data_end;
+ struct ethhdr *eth;
+ int err;
+
+ err = bpf_xdp_pull_data(ctx, sizeof(*eth), 0);
+ if (err)
+ return NULL;
+
+ data_end = (void *)(long)ctx->data_end;
+ data = eth = (void *)(long)ctx->data;
if (data + sizeof(*eth) > data_end)
return NULL;
if (eth->h_proto == bpf_htons(ETH_P_IP)) {
- struct iphdr *iph = data + sizeof(*eth);
+ struct iphdr *iph;
+
+ err = bpf_xdp_pull_data(ctx, sizeof(*eth) + sizeof(*iph) +
+ sizeof(*udph), 0);
+ if (err)
+ return NULL;
+
+ data_end = (void *)(long)ctx->data_end;
+ data = (void *)(long)ctx->data;
+
+ iph = data + sizeof(*eth);
if (iph + 1 > (struct iphdr *)data_end ||
iph->protocol != IPPROTO_UDP)
return NULL;
- udph = (void *)eth + sizeof(*iph) + sizeof(*eth);
- } else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
- struct ipv6hdr *ipv6h = data + sizeof(*eth);
+ udph = data + sizeof(*iph) + sizeof(*eth);
+ } else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
+ struct ipv6hdr *ipv6h;
+
+ err = bpf_xdp_pull_data(ctx, sizeof(*eth) + sizeof(*ipv6h) +
+ sizeof(*udph), 0);
+ if (err)
+ return NULL;
+
+ data_end = (void *)(long)ctx->data_end;
+ data = (void *)(long)ctx->data;
+
+ ipv6h = data + sizeof(*eth);
if (ipv6h + 1 > (struct ipv6hdr *)data_end ||
ipv6h->nexthdr != IPPROTO_UDP)
return NULL;
- udph = (void *)eth + sizeof(*ipv6h) + sizeof(*eth);
+ udph = data + sizeof(*ipv6h) + sizeof(*eth);
} else {
return NULL;
}
@@ -145,17 +175,34 @@ static void swap_machdr(void *data)
static int xdp_mode_tx_handler(struct xdp_md *ctx, __u16 port)
{
- void *data_end = (void *)(long)ctx->data_end;
- void *data = (void *)(long)ctx->data;
struct udphdr *udph = NULL;
- struct ethhdr *eth = data;
+ void *data, *data_end;
+ struct ethhdr *eth;
+ int err;
+
+ err = bpf_xdp_pull_data(ctx, sizeof(*eth), 0);
+ if (err)
+ return XDP_PASS;
+
+ data_end = (void *)(long)ctx->data_end;
+ data = eth = (void *)(long)ctx->data;
if (data + sizeof(*eth) > data_end)
return XDP_PASS;
if (eth->h_proto == bpf_htons(ETH_P_IP)) {
- struct iphdr *iph = data + sizeof(*eth);
- __be32 tmp_ip = iph->saddr;
+ struct iphdr *iph;
+ __be32 tmp_ip;
+
+ err = bpf_xdp_pull_data(ctx, sizeof(*eth) + sizeof(*iph) +
+ sizeof(*udph), 0);
+ if (err)
+ return XDP_PASS;
+
+ data_end = (void *)(long)ctx->data_end;
+ data = (void *)(long)ctx->data;
+
+ iph = data + sizeof(*eth);
if (iph + 1 > (struct iphdr *)data_end ||
iph->protocol != IPPROTO_UDP)
@@ -169,8 +216,10 @@ static int xdp_mode_tx_handler(struct xdp_md *ctx, __u16 port)
return XDP_PASS;
record_stats(ctx, STATS_RX);
+ eth = data;
swap_machdr((void *)eth);
+ tmp_ip = iph->saddr;
iph->saddr = iph->daddr;
iph->daddr = tmp_ip;
@@ -178,9 +227,19 @@ static int xdp_mode_tx_handler(struct xdp_md *ctx, __u16 port)
return XDP_TX;
- } else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
- struct ipv6hdr *ipv6h = data + sizeof(*eth);
+ } else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
struct in6_addr tmp_ipv6;
+ struct ipv6hdr *ipv6h;
+
+ err = bpf_xdp_pull_data(ctx, sizeof(*eth) + sizeof(*ipv6h) +
+ sizeof(*udph), 0);
+ if (err)
+ return XDP_PASS;
+
+ data_end = (void *)(long)ctx->data_end;
+ data = (void *)(long)ctx->data;
+
+ ipv6h = data + sizeof(*eth);
if (ipv6h + 1 > (struct ipv6hdr *)data_end ||
ipv6h->nexthdr != IPPROTO_UDP)
@@ -194,6 +253,7 @@ static int xdp_mode_tx_handler(struct xdp_md *ctx, __u16 port)
return XDP_PASS;
record_stats(ctx, STATS_RX);
+ eth = data;
swap_machdr((void *)eth);
__builtin_memcpy(&tmp_ipv6, &ipv6h->saddr, sizeof(tmp_ipv6));
--
2.47.3
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