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tap: Split tap specific and L2 (ethernet) headers

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In some places (well, actually only UDP now) we use struct tap_hdr to
represent both tap backend specific and L2 ethernet headers.  Handling
these together seemed like a good idea at the time, but Laurent's changes
in the TCP code working towards vhost-user support suggest that treating
them separately is more useful, more often.

Alter struct tap_hdr to represent only the TAP backend specific headers.
Updated related helpers and the UDP code to match.

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 16:53:45 +10:00 • committed by Stefano Brivio
parent c27ca91564
commit 34fb381b5a
2 changed files with 23 additions and 21 deletions

21
tap.h
View file

@ -6,30 +6,28 @@
#ifndef TAP_H
#define TAP_H
#define ETH_HDR_INIT(proto) { .h_proto = htons_constant(proto) }
/**
* struct tap_hdr - L2 and tap specific headers
* struct tap_hdr - tap backend specific headers
* @vnet_len: Frame length (for qemu socket transport)
* @eh: Ethernet header
*/
struct tap_hdr {
uint32_t vnet_len;
struct ethhdr eh;
} __attribute__((packed));
#define TAP_HDR_INIT(proto) { .eh.h_proto = htons_constant(proto) }
static inline size_t tap_hdr_len_(const struct ctx *c)
{
if (c->mode == MODE_PASST)
return sizeof(struct tap_hdr);
else
return sizeof(struct ethhdr);
return 0;
}
/**
* tap_frame_base() - Find start of tap frame
* @c: Execution context
* @taph: Pointer to L2 and tap specific header buffer
* @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())
@ -43,17 +41,16 @@ static inline void *tap_frame_base(const struct ctx *c, struct tap_hdr *taph)
* tap_frame_len() - Finalize tap frame and return total length
* @c: Execution context
* @taph: Tap header to finalize
* @plen: L3 packet length (excludes L2 and tap specific headers)
* @plen: L2 packet length (includes L2, excludes tap specific headers)
*
* Returns: length of the tap frame including L2 and tap specific
* headers - suitable for an iov_len to be passed to
* tap_send_frames()
* 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 + sizeof(taph->eh));
taph->vnet_len = htonl(plen);
return plen + tap_hdr_len_(c);
}