From: David Gibson <david@gibson.dropbear.id.au>
To: Stefano Brivio <sbrivio@redhat.com>, passt-dev@passt.top
Cc: Laurent Vivier <lvivier@redhat.com>,
David Gibson <david@gibson.dropbear.id.au>
Subject: [PATCH 1/4] tap: Extend tap_send_frames() to allow multi-buffer frames
Date: Fri, 8 Mar 2024 17:53:22 +1100 [thread overview]
Message-ID: <20240308065325.2181322-2-david@gibson.dropbear.id.au> (raw)
In-Reply-To: <20240308065325.2181322-1-david@gibson.dropbear.id.au>
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>
---
tap.c | 83 +++++++++++++++++++++++++++++++++++++----------------------
tap.h | 3 ++-
tcp.c | 8 +++---
udp.c | 2 +-
4 files changed, 59 insertions(+), 37 deletions(-)
diff --git a/tap.c b/tap.c
index f4051cec..f9e2a8d9 100644
--- a/tap.c
+++ b/tap.c
@@ -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 < nbufs && (buf_offset || (i % bufs_per_frame))) {
+ /* Number of not-fully-sent buffers in the frame */
+ size_t rembufs = bufs_per_frame - (i % bufs_per_frame);
- if (i < n && buf_offset) {
- /* A partial frame was sent */
- if (write_remainder(c->fd_tap, &iov[i], 1, buf_offset) < 0) {
+ 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;
}
diff --git a/tap.h b/tap.h
index 437b9aa2..c45aab3e 100644
--- a/tap.h
+++ b/tap.h
@@ -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);
diff --git a/tcp.c b/tcp.c
index d5eedf4d..9d90108b 100644
--- a/tcp.c
+++ b/tcp.c
@@ -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;
diff --git a/udp.c b/udp.c
index 45b7cc96..cba595c9 100644
--- a/udp.c
+++ b/udp.c
@@ -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);
}
/**
--
@@ -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);
}
/**
--
2.44.0
next prev parent reply other threads:[~2024-03-08 6:53 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-08 6:53 [PATCH 0/4] Some improvements to the tap send path David Gibson
2024-03-08 6:53 ` David Gibson [this message]
2024-03-14 7:02 ` [PATCH 1/4] tap: Extend tap_send_frames() to allow multi-buffer frames Stefano Brivio
2024-03-14 8:47 ` David Gibson
2024-03-08 6:53 ` [PATCH 2/4] tap: Simplify some casts in the tap "slow path" functions David Gibson
2024-03-08 6:53 ` [PATCH 3/4] tap: Implement tap_send() "slow path" in terms of fast path David Gibson
2024-03-08 6:53 ` [PATCH 4/4] tap: Rename tap_iov_{base,len} David Gibson
2024-03-08 8:18 ` [PATCH 0/4] Some improvements to the tap send path Laurent Vivier
2024-03-08 8:34 ` Stefano Brivio
2024-03-08 8:55 ` Laurent Vivier
2024-03-08 15:49 ` Laurent Vivier
2024-03-08 16:24 ` Stefano Brivio
2024-03-08 12:42 ` David Gibson
2024-03-08 16:49 ` Laurent Vivier
2024-03-09 4:15 ` David Gibson
2024-03-11 11:02 ` Laurent Vivier
2024-03-14 2:22 ` David Gibson
2024-03-14 16:40 ` Stefano Brivio
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