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

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Message-ID: <YrH86MxwX9VXnGbC@C02YVCJELVCG.dhcp.broadcom.net>
Date:   Tue, 21 Jun 2022 13:16:24 -0400
From:   Andy Gospodarek <andrew.gospodarek@...adcom.com>
To:     Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
Cc:     Andy Gospodarek <andrew.gospodarek@...adcom.com>, 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
Subject: Re: [PATCH net-next] samples/bpf: fixup some xdp progs to be able to
 support xdp multibuffer

On Tue, Jun 21, 2022 at 06:25:59PM +0200, Lorenzo Bianconi 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.
> > 
> > Signed-off-by: Andy Gospodarek <gospo@...adcom.com>
> 
> Hi Andy,
> 
> Just 2 nit inline but the code is fine.

Thanks, Lorenzo.  I'll re-spin now.


> 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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