On 21/06/2022 20:54, Andy Gospodarek wrote:
This changes the section name for the bpf program embedded in these
files to "xdp.frags" to allow the programs to be loaded on drivers that
are using an MTU greater than PAGE_SIZE. Rather than directly accessing
the buffers, the packet data is now accessed via xdp helper functions to
provide an example for those who may need to write more complex
programs.
v2: remove new unnecessary variable
Hi,
I'm trying to understand if there are any assumptions/requirements on
the length of the xdp_buf linear part when passed to XDP multi-buf programs?
Can the linear part be empty, with all data residing in the fragments?
Is it valid?
Per the proposed pattern below (calling bpf_xdp_load_bytes() to memcpy
packet data into a local buffer), no such assumption is required, and an
xdp_buf created by the driver with an empty linear part is valid.
However, in the _xdp_tx_iptunnel example program, it fails (returns
XDP_DROP) in case the headers are not in the linear part.
Regards,
Tariq
Signed-off-by: Andy Gospodarek <gospo@xxxxxxxxxxxx>
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Acked-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
---
samples/bpf/xdp1_kern.c | 11 ++++++++---
samples/bpf/xdp2_kern.c | 11 ++++++++---
samples/bpf/xdp_tx_iptunnel_kern.c | 2 +-
3 files changed, 17 insertions(+), 7 deletions(-)
diff --git a/samples/bpf/xdp1_kern.c b/samples/bpf/xdp1_kern.c
index f0c5d95084de..0a5c704badd0 100644
--- a/samples/bpf/xdp1_kern.c
+++ b/samples/bpf/xdp1_kern.c
@@ -39,11 +39,13 @@ static int parse_ipv6(void *data, u64 nh_off, void *data_end)
return ip6h->nexthdr;
}
-SEC("xdp1")
+#define XDPBUFSIZE 64
+SEC("xdp.frags")
int xdp_prog1(struct xdp_md *ctx)
{
- void *data_end = (void *)(long)ctx->data_end;
- void *data = (void *)(long)ctx->data;
+ __u8 pkt[XDPBUFSIZE] = {};
+ void *data_end = &pkt[XDPBUFSIZE-1];
+ void *data = pkt;
struct ethhdr *eth = data;
int rc = XDP_DROP;
long *value;
@@ -51,6 +53,9 @@ int xdp_prog1(struct xdp_md *ctx)
u64 nh_off;
u32 ipproto;
+ if (bpf_xdp_load_bytes(ctx, 0, pkt, sizeof(pkt)))
+ return rc;
+
nh_off = sizeof(*eth);
if (data + nh_off > data_end)
return rc;
diff --git a/samples/bpf/xdp2_kern.c b/samples/bpf/xdp2_kern.c
index d8a64ab077b0..3332ba6bb95f 100644
--- a/samples/bpf/xdp2_kern.c
+++ b/samples/bpf/xdp2_kern.c
@@ -55,11 +55,13 @@ static int parse_ipv6(void *data, u64 nh_off, void *data_end)
return ip6h->nexthdr;
}
-SEC("xdp1")
+#define XDPBUFSIZE 64
+SEC("xdp.frags")
int xdp_prog1(struct xdp_md *ctx)
{
- void *data_end = (void *)(long)ctx->data_end;
- void *data = (void *)(long)ctx->data;
+ __u8 pkt[XDPBUFSIZE] = {};
+ void *data_end = &pkt[XDPBUFSIZE-1];
+ void *data = pkt;
struct ethhdr *eth = data;
int rc = XDP_DROP;
long *value;
@@ -67,6 +69,9 @@ int xdp_prog1(struct xdp_md *ctx)
u64 nh_off;
u32 ipproto;
+ if (bpf_xdp_load_bytes(ctx, 0, pkt, sizeof(pkt)))
+ return rc;
+
nh_off = sizeof(*eth);
if (data + nh_off > data_end)
return rc;
diff --git a/samples/bpf/xdp_tx_iptunnel_kern.c b/samples/bpf/xdp_tx_iptunnel_kern.c
index 575d57e4b8d6..0e2bca3a3fff 100644
--- a/samples/bpf/xdp_tx_iptunnel_kern.c
+++ b/samples/bpf/xdp_tx_iptunnel_kern.c
@@ -212,7 +212,7 @@ static __always_inline int handle_ipv6(struct xdp_md *xdp)
return XDP_TX;
}
-SEC("xdp_tx_iptunnel")
+SEC("xdp.frags")
int _xdp_tx_iptunnel(struct xdp_md *xdp)
{
void *data_end = (void *)(long)xdp->data_end;
