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tap: Use different io vector bases depending on tap type

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Currently tap_send_frames() expects the frames it is given to include the
vnet_len field, even in pasta mode which doesn't use it (although it need
not be initialized in that case).  To match, tap_iov_base() and
tap_iov_len() construct the frame in that way.

This will inconvenience future changes, so alter things to set the buffers
to include just the frame needed by the tap backend type.

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 2023-01-06 11:43:19 +11:00 committed by Stefano Brivio
parent 2416310a17
commit 0fb7b2b908
2 changed files with 6 additions and 5 deletions
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5
tap.c
View file

@ -317,8 +317,7 @@ static void tap_send_frames_pasta(struct ctx *c,
size_t i; size_t i;
for (i = 0; i < n; i++) { for (i = 0; i < n; i++) {
if (write(c->fd_tap, (char *)iov->iov_base + 4, if (write(c->fd_tap, (char *)iov->iov_base, iov->iov_len) < 0) {
iov->iov_len - 4) < 0) {
debug("tap write: %s", strerror(errno)); debug("tap write: %s", strerror(errno));
if (errno != EAGAIN && errno != EWOULDBLOCK) if (errno != EAGAIN && errno != EWOULDBLOCK)
tap_handler(c, c->fd_tap, EPOLLERR, NULL); tap_handler(c, c->fd_tap, EPOLLERR, NULL);
@ -383,7 +382,7 @@ void tap_send_frames(struct ctx *c, const struct iovec *iov, size_t n)
else else
tap_send_frames_pasta(c, iov, n); tap_send_frames_pasta(c, iov, n);
pcap_multiple(iov, n, sizeof(uint32_t)); pcap_multiple(iov, n, c->mode == MODE_PASST ? sizeof(uint32_t) : 0);
} }
/** /**

6
tap.h
View file

@ -20,8 +20,10 @@ struct tap_hdr {
static inline size_t tap_hdr_len_(const struct ctx *c) static inline size_t tap_hdr_len_(const struct ctx *c)
{ {
(void)c; if (c->mode == MODE_PASST)
return sizeof(struct tap_hdr); return sizeof(struct tap_hdr);
else
return sizeof(struct ethhdr);
} }
/** /**