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udp: Split tap-bound UDP packets into multiple buffers using io vector

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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>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson
2024-05-01 18:31:05 +10:00
committed by Stefano Brivio
parent fcd9308856
commit 3f9bd867b5
2 changed files with 49 additions and 63 deletions
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38
tap.h
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@@ -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
* @l2len: 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 l2len)
{
if (c->mode == MODE_PASST)
taph->vnet_len = htonl(l2len);
return l2len + 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,