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tap: Extend tap_send_frames() to allow multi-buffer frames

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tap_send_frames() takes a vector of buffers and requires exactly one frame
per buffer.  We have future plans where we want to have multiple buffers
per frame in some circumstances, so extend tap_send_frames() to take the
number of buffers per frame as a parameter.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Improve comment to rembufs calculation]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2024-03-08 17:53:22 +11:00 committed by Stefano Brivio
parent f67238aa86
commit 2d0e0084b6
4 changed files with 59 additions and 37 deletions
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83
tap.c
View File

@ -309,21 +309,28 @@ void tap_icmp6_send(const struct ctx *c,
/**
* tap_send_frames_pasta() - Send multiple frames to the pasta tap
* @c: Execution context
* @iov: Array of buffers, each containing one frame
* @n: Number of buffers/frames in @iov
* @c: Execution context
* @iov: Array of buffers
* @bufs_per_frame: Number of buffers (iovec entries) per frame
* @nframes: Number of frames to send
*
* @iov must have total length @bufs_per_frame * @nframes, with each set of
* @bufs_per_frame contiguous buffers representing a single frame.
*
* Return: number of frames successfully sent
*
* #syscalls:pasta write
*/
static size_t tap_send_frames_pasta(const struct ctx *c,
const struct iovec *iov, size_t n)
const struct iovec *iov,
size_t bufs_per_frame, size_t nframes)
{
size_t nbufs = bufs_per_frame * nframes;
size_t i;
for (i = 0; i < n; i++) {
ssize_t rc = write(c->fd_tap, iov[i].iov_base, iov[i].iov_len);
for (i = 0; i < nbufs; i += bufs_per_frame) {
ssize_t rc = writev(c->fd_tap, iov + i, bufs_per_frame);
size_t framelen = iov_size(iov + i, bufs_per_frame);
if (rc < 0) {
debug("tap write: %s", strerror(errno));
@ -340,32 +347,37 @@ static size_t tap_send_frames_pasta(const struct ctx *c,
default:
die("Write error on tap device, exiting");
}
} else if ((size_t)rc < iov[i].iov_len) {
debug("short write on tuntap: %zd/%zu",
rc, iov[i].iov_len);
} else if ((size_t)rc < framelen) {
debug("short write on tuntap: %zd/%zu", rc, framelen);
break;
}
}
return i;
return i / bufs_per_frame;
}
/**
* tap_send_frames_passt() - Send multiple frames to the passt tap
* @c: Execution context
* @iov: Array of buffers, each containing one frame
* @n: Number of buffers/frames in @iov
* @c: Execution context
* @iov: Array of buffers, each containing one frame
* @bufs_per_frame: Number of buffers (iovec entries) per frame
* @nframes: Number of frames to send
*
* @iov must have total length @bufs_per_frame * @nframes, with each set of
* @bufs_per_frame contiguous buffers representing a single frame.
*
* Return: number of frames successfully sent
*
* #syscalls:passt sendmsg
*/
static size_t tap_send_frames_passt(const struct ctx *c,
const struct iovec *iov, size_t n)
const struct iovec *iov,
size_t bufs_per_frame, size_t nframes)
{
size_t nbufs = bufs_per_frame * nframes;
struct msghdr mh = {
.msg_iov = (void *)iov,
.msg_iovlen = n,
.msg_iovlen = nbufs,
};
size_t buf_offset;
unsigned int i;
@ -376,44 +388,53 @@ static size_t tap_send_frames_passt(const struct ctx *c,
return 0;
/* Check for any partial frames due to short send */
i = iov_skip_bytes(iov, n, sent, &buf_offset);
i = iov_skip_bytes(iov, nbufs, sent, &buf_offset);
if (i < n && buf_offset) {
/* A partial frame was sent */
if (write_remainder(c->fd_tap, &iov[i], 1, buf_offset) < 0) {
if (i < nbufs && (buf_offset || (i % bufs_per_frame))) {
/* Number of unsent or partially sent buffers for the frame */
size_t rembufs = bufs_per_frame - (i % bufs_per_frame);
if (write_remainder(c->fd_tap, &iov[i], rembufs, buf_offset) < 0) {
err("tap: partial frame send: %s", strerror(errno));
return i;
}
i++;
i += rembufs;
}
return i;
return i / bufs_per_frame;
}
/**
* tap_send_frames() - Send out multiple prepared frames
* @c: Execution context
* @iov: Array of buffers, each containing one frame (with L2 headers)
* @n: Number of buffers/frames in @iov
* @c: Execution context
* @iov: Array of buffers, each containing one frame (with L2 headers)
* @bufs_per_frame: Number of buffers (iovec entries) per frame
* @nframes: Number of frames to send
*
* @iov must have total length @bufs_per_frame * @nframes, with each set of
* @bufs_per_frame contiguous buffers representing a single frame.
*
* Return: number of frames actually sent
*/
size_t tap_send_frames(const struct ctx *c, const struct iovec *iov, size_t n)
size_t tap_send_frames(const struct ctx *c, const struct iovec *iov,
size_t bufs_per_frame, size_t nframes)
{
size_t m;
if (!n)
if (!nframes)
return 0;
if (c->mode == MODE_PASST)
m = tap_send_frames_passt(c, iov, n);
m = tap_send_frames_passt(c, iov, bufs_per_frame, nframes);
else
m = tap_send_frames_pasta(c, iov, n);
m = tap_send_frames_pasta(c, iov, bufs_per_frame, nframes);
if (m < n)
debug("tap: failed to send %zu frames of %zu", n - m, n);
if (m < nframes)
debug("tap: failed to send %zu frames of %zu",
nframes - m, nframes);
pcap_multiple(iov, 1, m, c->mode == MODE_PASST ? sizeof(uint32_t) : 0);
pcap_multiple(iov, bufs_per_frame, m,
c->mode == MODE_PASST ? sizeof(uint32_t) : 0);
return m;
}

3
tap.h
View File

@ -73,7 +73,8 @@ void tap_icmp6_send(const struct ctx *c,
const struct in6_addr *src, const struct in6_addr *dst,
const void *in, size_t len);
int tap_send(const struct ctx *c, const void *data, size_t len);
size_t tap_send_frames(const struct ctx *c, const struct iovec *iov, size_t n);
size_t tap_send_frames(const struct ctx *c, const struct iovec *iov,
size_t bufs_per_frame, size_t nframes);
void eth_update_mac(struct ethhdr *eh,
const unsigned char *eth_d, const unsigned char *eth_s);
void tap_listen_handler(struct ctx *c, uint32_t events);

8
tcp.c
View File

@ -1289,10 +1289,10 @@ static void tcp_rst_do(struct ctx *c, struct tcp_tap_conn *conn);
*/
static void tcp_l2_flags_buf_flush(const struct ctx *c)
{
tap_send_frames(c, tcp6_l2_flags_iov, tcp6_l2_flags_buf_used);
tap_send_frames(c, tcp6_l2_flags_iov, 1, tcp6_l2_flags_buf_used);
tcp6_l2_flags_buf_used = 0;
tap_send_frames(c, tcp4_l2_flags_iov, tcp4_l2_flags_buf_used);
tap_send_frames(c, tcp4_l2_flags_iov, 1, tcp4_l2_flags_buf_used);
tcp4_l2_flags_buf_used = 0;
}
@ -1305,12 +1305,12 @@ static void tcp_l2_data_buf_flush(const struct ctx *c)
unsigned i;
size_t m;
m = tap_send_frames(c, tcp6_l2_iov, tcp6_l2_buf_used);
m = tap_send_frames(c, tcp6_l2_iov, 1, tcp6_l2_buf_used);
for (i = 0; i < m; i++)
*tcp6_l2_buf_seq_update[i].seq += tcp6_l2_buf_seq_update[i].len;
tcp6_l2_buf_used = 0;
m = tap_send_frames(c, tcp4_l2_iov, tcp4_l2_buf_used);
m = tap_send_frames(c, tcp4_l2_iov, 1, tcp4_l2_buf_used);
for (i = 0; i < m; i++)
*tcp4_l2_buf_seq_update[i].seq += tcp4_l2_buf_seq_update[i].len;
tcp4_l2_buf_used = 0;

2
udp.c
View File

@ -712,7 +712,7 @@ static void udp_tap_send(const struct ctx *c,
tap_iov[i].iov_len = buf_len;
}
tap_send_frames(c, tap_iov + start, n);
tap_send_frames(c, tap_iov + start, 1, n);
}
/**