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

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(a)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(a)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