Re: [PATCH 2/7] udp: Split tap-bound UDP packets into multiple buffers using io vector

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Apr 30, 2024 at 10:15:34PM +0200, Stefano Brivio wrote:
> On Tue, 30 Apr 2024 20:05:36 +1000
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > When sending to the tap device, currently we assemble the headers and
> > payload into a single contiguous buffer.  Those are described by a single
> > struct iovec, then a batch of frames is sent to the device with
> > tap_send_frames().
> > 
> > In order to better integrate the IPv4 and IPv6 paths, we want the IP
> > header in a different buffer that might not be contiguous with the
> > payload.  To prepare for that, split the UDP packet into an iovec of
> > buffers.  We use the same split that Laurent recently introduced for
> > TCP for convenience.
> > 
> > This removes the last use of tap_hdr_len_(), tap_frame_base() and
> > tap_frame_len(), so remove those too.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  tap.h | 38 ------------------------------
> >  udp.c | 74 +++++++++++++++++++++++++++++++++++++++--------------------
> >  2 files changed, 49 insertions(+), 63 deletions(-)
> > 
> > diff --git a/tap.h b/tap.h
> > index 75aa3f03..754703d2 100644
> > --- a/tap.h
> > +++ b/tap.h
> > @@ -43,44 +43,6 @@ static inline void tap_hdr_update(struct tap_hdr *thdr, size_t l2len)
> >  	thdr->vnet_len = htonl(l2len);
> >  }
> >  
> > -static inline size_t tap_hdr_len_(const struct ctx *c)
> > -{
> > -	if (c->mode == MODE_PASST)
> > -		return sizeof(struct tap_hdr);
> > -	else
> > -		return 0;
> > -}
> > -
> > -/**
> > - * tap_frame_base() - Find start of tap frame
> > - * @c:		Execution context
> > - * @taph:	Pointer to tap specific header buffer
> > - *
> > - * Returns: pointer to the start of tap frame - suitable for an
> > - *          iov_base to be passed to tap_send_frames())
> > - */
> > -static inline void *tap_frame_base(const struct ctx *c, struct tap_hdr *taph)
> > -{
> > -	return (char *)(taph + 1) - tap_hdr_len_(c);
> > -}
> > -
> > -/**
> > - * tap_frame_len() - Finalize tap frame and return total length
> > - * @c:		Execution context
> > - * @taph:	Tap header to finalize
> > - * @plen:	L2 packet length (includes L2, excludes tap specific headers)
> > - *
> > - * Returns: length of the tap frame including tap specific headers - suitable
> > - *          for an iov_len to be passed to tap_send_frames()
> > - */
> > -static inline size_t tap_frame_len(const struct ctx *c, struct tap_hdr *taph,
> > -				   size_t plen)
> > -{
> > -	if (c->mode == MODE_PASST)
> > -		taph->vnet_len = htonl(plen);
> > -	return plen + tap_hdr_len_(c);
> > -}
> > -
> >  struct in_addr tap_ip4_daddr(const struct ctx *c);
> >  void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
> >  		   struct in_addr dst, in_port_t dport,
> > diff --git a/udp.c b/udp.c
> > index 545212c5..4650b366 100644
> > --- a/udp.c
> > +++ b/udp.c
> > @@ -222,12 +222,28 @@ struct udp6_l2_buf_t {
> >  #endif
> >  udp6_l2_buf[UDP_MAX_FRAMES];
> >  
> > +/**
> > + * enum udp_iov_idx - Indices for the buffers making up a single UDP frame
> > + * @UDP_IOV_TAP         TAP specific header
> 
> Nits: s/TAP/tap/ and
> 
> > + * @UDP_IOV_ETH         ethernet header
> 
> s/ethernet/Ethernet.

Amended, thanks.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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