From 2d0e0084b60851f3d032d9b91454fcbebfb67061 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Fri, 8 Mar 2024 17:53:22 +1100 Subject: tap: Extend tap_send_frames() to allow multi-buffer frames 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 [sbrivio: Improve comment to rembufs calculation] Signed-off-by: Stefano Brivio --- tap.c | 83 ++++++++++++++++++++++++++++++++++++++++++------------------------- 1 file changed, 52 insertions(+), 31 deletions(-) (limited to 'tap.c') diff --git a/tap.c b/tap.c index f4051ce..8e0cda3 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 < 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; } -- cgit v1.2.3