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From: Stephen Hemminger <stephen@networkplumber.org>
To: Chas Williams <3chas3@gmail.com>
Cc: dev@dpdk.org, Stephen Hemminger <sthemmin@microsoft.com>
Subject: Re: [dpdk-dev] [PATCH] net: fix rte_vlan_insert with shared mbuf
Date: Wed, 27 Mar 2019 08:18:38 -0700	[thread overview]
Message-ID: <20190327081838.46c46907@shemminger-XPS-13-9360> (raw)
Message-ID: <20190327151838.FWsxM1kDyW6PXA-hx0xWaeOBJolVAX92oFTDFN3eL74@z> (raw)
In-Reply-To: <0889dffe-e9d8-f480-0480-5b9950fcbbf9@gmail.com>

On Tue, 26 Mar 2019 18:38:57 -0400
Chas Williams <3chas3@gmail.com> wrote:

> On 3/26/19 3:15 PM, Stephen Hemminger wrote:
> > If mbuf refcnt was > 1 then rte_vlan_insert() would incorrectly
> > modify the original copy. Original code was expecting clone to make
> > a copy (it doesn't). Better to let the caller deal with making
> > a copy or setting up mbuf chain to allow for header to be added.
> > 
> > Also fix docbook comment about parameters (function takes
> > pointer to mbuf).
> > 
> > Fixes: c974021a5949 ("ether: add soft vlan encap/decap")
> > Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
> > ---
> >   lib/librte_net/rte_ether.h | 15 ++++-----------
> >   1 file changed, 4 insertions(+), 11 deletions(-)
> > 
> > diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h
> > index c2c5e249ffe9..bab2b198fa79 100644
> > --- a/lib/librte_net/rte_ether.h
> > +++ b/lib/librte_net/rte_ether.h
> > @@ -374,7 +374,7 @@ static inline int rte_vlan_strip(struct rte_mbuf *m)
> >    * Software version of VLAN unstripping
> >    *
> >    * @param m
> > - *   The packet mbuf.
> > + *   Pointer to the packet mbuf.
> >    * @return
> >    *   - 0: On success
> >    *   -EPERM: mbuf is is shared overwriting would be unsafe
> > @@ -385,16 +385,9 @@ static inline int rte_vlan_insert(struct rte_mbuf **m)
> >   	struct ether_hdr *oh, *nh;
> >   	struct vlan_hdr *vh;
> >   
> > -	/* Can't insert header if mbuf is shared */
> > -	if (rte_mbuf_refcnt_read(*m) > 1) {
> > -		struct rte_mbuf *copy;
> > -
> > -		copy = rte_pktmbuf_clone(*m, (*m)->pool);
> > -		if (unlikely(copy == NULL))
> > -			return -ENOMEM;
> > -		rte_pktmbuf_free(*m);
> > -		*m = copy;
> > -	}
> > +	/* Can't directly insert header if mbuf is shared */
> > +	if (rte_mbuf_refcnt_read(*m) > 1)  
> 
> This check probably isn't sufficient. You need something more like:
> 
>          if (rte_mbuf_refcnt_read(mbuf) > 1 ||
>              (RTE_MBUF_INDIRECT(mbuf) &&
>               rte_mbuf_refcnt_read(rte_mbuf_from_indirect(mbuf)) > 1)) {
> 
> If this is a cloned packet, the refcnt will be 1. So you need to examine 
> the parent mbuf to see if other clones exist.
> 

The problem is that indirect buffers probably can't be overwritten
because of lack of headroom.

Actually, why not push the problem into the pktmbuf_headroom logic?

  parent reply	other threads:[~2019-03-27 15:18 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-26 19:15 Stephen Hemminger
2019-03-26 19:15 ` Stephen Hemminger
2019-03-26 22:38 ` Chas Williams
2019-03-26 22:38   ` Chas Williams
2019-03-27 15:18   ` Stephen Hemminger [this message]
2019-03-27 15:18     ` Stephen Hemminger
2019-03-27 15:31     ` Chas Williams
2019-03-27 15:31       ` Chas Williams
2019-03-28 14:04       ` Ferruh Yigit
2019-03-28 14:04         ` Ferruh Yigit
2019-03-28 20:53         ` [dpdk-dev] [RFC v2] " Stephen Hemminger
2019-03-28 20:53           ` Stephen Hemminger
2019-03-30 12:41           ` Chas Williams
2019-03-30 12:41             ` Chas Williams
2019-04-04 23:54             ` Stephen Hemminger
2019-04-04 23:54               ` Stephen Hemminger
2019-04-06 23:11               ` Chas Williams
2019-04-06 23:11                 ` Chas Williams
2019-04-12 16:35           ` Ferruh Yigit
2019-04-12 16:35             ` Ferruh Yigit
2019-07-04 18:40             ` Ferruh Yigit

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