netdev - Re: [PATCH net-next] samples/bpf: fixup some xdp progs to be able to support xdp multibuffer

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Date:   Tue, 21 Jun 2022 18:25:59 +0200
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     Andy Gospodarek <andrew.gospodarek@...adcom.com>
Cc:     ast@...nel.org, daniel@...earbox.net, davem@...emloft.net,
        kuba@...nel.org, hawk@...nel.org, john.fastabend@...il.com,
        andrii@...nel.org, kafai@...com, songliubraving@...com, yhs@...com,
        kpsingh@...nel.org, toke@...hat.com, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Andy Gospodarek <gospo@...adcom.com>
Subject: Re: [PATCH net-next] samples/bpf: fixup some xdp progs to be able to
 support xdp multibuffer

> 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.
> 
> Signed-off-by: Andy Gospodarek <gospo@...adcom.com>

Hi Andy,

Just 2 nit inline but the code is fine.

Acked-by: Lorenzo Bianconi <lorenzo@...nel.org>

> ---
>  samples/bpf/xdp1_kern.c            | 13 ++++++++++---
>  samples/bpf/xdp2_kern.c            | 13 ++++++++++---
>  samples/bpf/xdp_tx_iptunnel_kern.c |  2 +-
>  3 files changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/samples/bpf/xdp1_kern.c b/samples/bpf/xdp1_kern.c
> index f0c5d95084de..a798553fca3b 100644
> --- a/samples/bpf/xdp1_kern.c
> +++ b/samples/bpf/xdp1_kern.c
> @@ -39,17 +39,24 @@ 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;
>  	u16 h_proto;
>  	u64 nh_off;
>  	u32 ipproto;
> +	int err;
> +
> +	err = bpf_xdp_load_bytes(ctx, 0, pkt, sizeof(pkt));
> +	if (err < 0)
> +		return rc;

I guess we do not need err here:

	if (bpf_xdp_load_bytes(ctx, 0, pkt, sizeof(pkt)) < 0)
		return XDP_DROP;

>  
>  	nh_off = sizeof(*eth);
>  	if (data + nh_off > data_end)
> diff --git a/samples/bpf/xdp2_kern.c b/samples/bpf/xdp2_kern.c
> index d8a64ab077b0..1502ef820aed 100644
> --- a/samples/bpf/xdp2_kern.c
> +++ b/samples/bpf/xdp2_kern.c
> @@ -55,17 +55,24 @@ 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;
>  	u16 h_proto;
>  	u64 nh_off;
>  	u32 ipproto;
> +	int err;
> +
> +	err = bpf_xdp_load_bytes(ctx, 0, pkt, sizeof(pkt));
> +	if (err < 0)
> +		return rc;

same here

>  
>  	nh_off = sizeof(*eth);
>  	if (data + nh_off > data_end)
> 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;
> -- 
> 2.25.1
> 



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