From a6e919a9511402bd45d7fc80540c1f93166cb4af Mon Sep 17 00:00:00 2001 From: David Gibson Date: Thu, 5 Jan 2023 15:26:18 +1100 Subject: udp: Move sending pasta tap frames to the end of udp_sock_handler() udp_sock_handler() has a surprising difference in flow between pasta and passt mode: For pasta we send each frame to the tap interface as we prepare it. For passt, though, we prepare all the frames, then send them with a single sendmmsg(). Alter the pasta path to also prepare all the frames, then send them at the end. We already have a suitable data structure for the passt case. This will make it easier to abstract out the tap backend difference in future. Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- udp.c | 61 ++++++++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 42 insertions(+), 19 deletions(-) diff --git a/udp.c b/udp.c index 4610a02..a27fe88 100644 --- a/udp.c +++ b/udp.c @@ -783,6 +783,35 @@ static size_t udp_update_hdr6(const struct ctx *c, int n, in_port_t dstport, return buf_len; } +/** + * udp_tap_send_pasta() - Send datagrams to the pasta tap interface + * @c: Execution context + * @mmh: Array of message headers to send + * @n: Number of message headers to send + * + * #syscalls:pasta write + */ +static void udp_tap_send_pasta(const struct ctx *c, struct mmsghdr *mmh, + unsigned int n) +{ + unsigned int i, j; + + for (i = 0; i < n; i++) { + for (j = 0; j < mmh[i].msg_hdr.msg_iovlen; j++) { + struct iovec *iov = &mmh[i].msg_hdr.msg_iov[j]; + + /* We can't use writev() because the tap + * character device relies on the write() + * boundaries to discern frame boundaries + */ + if (write(c->fd_tap, iov->iov_base, iov->iov_len) < 0) + debug("tap write: %s", strerror(errno)); + else + pcap(iov->iov_base, iov->iov_len); + } + } +} + /** * udp_sock_handler() - Handle new data from socket * @c: Execution context @@ -835,31 +864,25 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events, else buf_len = udp_update_hdr4(c, i, dstport, now); - if (c->mode == MODE_PASTA) { - void *frame = tap_iov[i].iov_base; + tap_iov[i].iov_len = buf_len; - if (write(c->fd_tap, frame, buf_len) < 0) - debug("tap write: %s", strerror(errno)); - pcap(frame, buf_len); - } else { - tap_iov[i].iov_len = buf_len; - - /* With bigger messages, qemu closes the connection. */ - if (msg_bufs && msg_len + buf_len > SHRT_MAX) { - tap_mmh[msg_i].msg_hdr.msg_iovlen = msg_bufs; - msg_i++; - tap_mmh[msg_i].msg_hdr.msg_iov = &tap_iov[i]; - msg_len = msg_bufs = 0; - } - - msg_len += buf_len; - msg_bufs++; + /* With bigger messages, qemu closes the connection. */ + if (c->mode == MODE_PASST && msg_bufs && + msg_len + buf_len > SHRT_MAX) { + tap_mmh[msg_i].msg_hdr.msg_iovlen = msg_bufs; + msg_i++; + tap_mmh[msg_i].msg_hdr.msg_iov = &tap_iov[i]; + msg_len = msg_bufs = 0; } + msg_len += buf_len; + msg_bufs++; } tap_mmh[msg_i].msg_hdr.msg_iovlen = msg_bufs; - if (c->mode == MODE_PASTA) + if (c->mode == MODE_PASTA) { + udp_tap_send_pasta(c, tap_mmh, msg_i + 1); return; + } ret = sendmmsg(c->fd_tap, tap_mmh, msg_i + 1, MSG_NOSIGNAL | MSG_DONTWAIT); -- cgit v1.2.3