Re: [PATCH 4/5] ebpf_rss_helper: Added helper for eBPF RSS.

On Fri, Aug 20, 2021 at 6:41 AM Jason Wang <jasowang@redhat.com> wrote:

在 2021/7/13 下午11:37, Andrew Melnychenko 写道:
> Helper program. Loads eBPF RSS program and maps and passes them through unix socket.
> Libvirt may launch this helper and pass eBPF fds to qemu virtio-net.

I wonder if this can be done as helper for TAP/bridge.

E.g it's the qemu to launch those helper with set-uid.

Then libvirt won't even need to care about that?

> Also, libbpf dependency now exclusively for Linux.
> Libbpf is used for eBPF RSS steering, which is supported only by Linux TAP.
> There is no reason yet to build eBPF loader and helper for non Linux systems,
> even if libbpf is present.
>
> Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
> ---
> ebpf/qemu-ebpf-rss-helper.c | 130 ++++++++++++++++++++++++++++++++++++
> meson.build | 37 ++++++----
> 2 files changed, 154 insertions(+), 13 deletions(-)
> create mode 100644 ebpf/qemu-ebpf-rss-helper.c
>
> diff --git a/ebpf/qemu-ebpf-rss-helper.c b/ebpf/qemu-ebpf-rss-helper.c
> new file mode 100644
> index 0000000000..fe68758f57
> --- /dev/null
> +++ b/ebpf/qemu-ebpf-rss-helper.c
> @@ -0,0 +1,130 @@
> +/*
> + * eBPF RSS Helper
> + *
> + * Developed by Daynix Computing LTD (http://www.daynix.com)
> + *
> + * Authors:
> + * Andrew Melnychenko <andrew@daynix.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2. See
> + * the COPYING file in the top-level directory.
> + *
> + * Description: This is helper program for libvirtd.
> + * It loads eBPF RSS program and passes fds through unix socket.
> + * Built by meson, target - 'qemu-ebpf-rss-helper'.
> + */
> +
> +#include <stdio.h>
> +#include <stdint.h>
> +#include <stdlib.h>
> +#include <stdbool.h>
> +#include <getopt.h>
> +#include <memory.h>
> +#include <errno.h>
> +#include <sys/socket.h>
> +
> +#include "ebpf_rss.h"
> +
> +#include "qemu-helper-stamp.h"
> +
> +void QEMU_HELPER_STAMP(void) {}
> +
> +static int send_fds(int socket, int *fds, int n)
> +{
> + struct msghdr msg = {};
> + struct cmsghdr *cmsg = NULL;
> + char buf[CMSG_SPACE(n * sizeof(int))];
> + char dummy_buffer = 0;
> + struct iovec io = { .iov_base = &dummy_buffer,
> + .iov_len = sizeof(dummy_buffer) };
> +
> + memset(buf, 0, sizeof(buf));
> +
> + msg.msg_iov = &io;
> + msg.msg_iovlen = 1;
> + msg.msg_control = buf;
> + msg.msg_controllen = sizeof(buf);
> +
> + cmsg = CMSG_FIRSTHDR(&msg);
> + cmsg->cmsg_level = SOL_SOCKET;
> + cmsg->cmsg_type = SCM_RIGHTS;
> + cmsg->cmsg_len = CMSG_LEN(n * sizeof(int));
> +
> + memcpy(CMSG_DATA(cmsg), fds, n * sizeof(int));
> +
> + return sendmsg(socket, &msg, 0);
> +}
> +
> +static void print_help_and_exit(const char *prog, int exitcode)
> +{
> + fprintf(stderr, "%s - load eBPF RSS program for qemu and pass eBPF fds"
> + " through unix socket.\n", prog);
> + fprintf(stderr, "\t--fd <num>, -f <num> - unix socket file descriptor"
> + " used to pass eBPF fds.\n");
> + fprintf(stderr, "\t--help, -h - this help.\n");
> + exit(exitcode);
> +}
> +
> +int main(int argc, char **argv)
> +{
> + char *fd_string = NULL;
> + int unix_fd = 0;
> + struct EBPFRSSContext ctx = {};
> + int fds[EBPF_RSS_MAX_FDS] = {};
> + int ret = -1;
> +
> + for (;;) {
> + int c;
> + static struct option long_options[] = {
> + {"help", no_argument, 0, 'h'},
> + {"fd", required_argument, 0, 'f'},
> + {0, 0, 0, 0}
> + };
> + c = getopt_long(argc, argv, "hf:",
> + long_options, NULL);
> +
> + if (c == -1) {
> + break;
> + }
> +
> + switch (c) {
> + case 'f':
> + fd_string = optarg;
> + break;
> + case 'h':
> + default:
> + print_help_and_exit(argv[0],
> + c == 'h' ? EXIT_SUCCESS : EXIT_FAILURE);
> + }
> + }
> +
> + if (!fd_string) {
> + fprintf(stderr, "Unix file descriptor not present.\n");
> + print_help_and_exit(argv[0], EXIT_FAILURE);
> + }
> +
> + unix_fd = atoi(fd_string);
> +
> + if (!unix_fd) {
> + fprintf(stderr, "Unix file descriptor is invalid.\n");
> + return EXIT_FAILURE;
> + }
> +
> + ebpf_rss_init(&ctx);
> + if (!ebpf_rss_load(&ctx)) {
> + fprintf(stderr, "Can't load ebpf.\n");
> + return EXIT_FAILURE;
> + }
> + fds[0] = ctx.program_fd;
> + fds[1] = ctx.map_configuration;
> +
> + ret = send_fds(unix_fd, fds, EBPF_RSS_MAX_FDS);
> + if (ret < 0) {
> + fprintf(stderr, "Issue while sending fds: %s.\n", strerror(errno));
> + }
> +
> + ebpf_rss_unload(&ctx);
> +
> + return ret < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
> +}
> +
> diff --git a/meson.build b/meson.build
> index 257e51d91b..913aa1fee5 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -1033,19 +1033,22 @@ if not get_option('fuse_lseek').disabled()
> endif
>
> # libbpf
> -libbpf = dependency('libbpf', required: get_option('bpf'), method: 'pkg-config')
> -if libbpf.found() and not cc.links('''
> - #include <bpf/libbpf.h>
> - int main(void)
> - {
> - bpf_object__destroy_skeleton(NULL);
> - return 0;
> - }''', dependencies: libbpf)
> - libbpf = not_found
> - if get_option('bpf').enabled()
> - error('libbpf skeleton test failed')
> - else
> - warning('libbpf skeleton test failed, disabling')
> +libbpf = not_found
> +if targetos == 'linux'
> + libbpf = dependency('libbpf', required: get_option('bpf'), method: 'pkg-config')
> + if libbpf.found() and not cc.links('''
> + #include <bpf/libbpf.h>
> + int main(void)
> + {
> + bpf_object__destroy_skeleton(NULL);

Do we need to test whether the bpf can do mmap() here?

Thanks

> + return 0;
> + }''', dependencies: libbpf)
> + libbpf = not_found
> + if get_option('bpf').enabled()
> + error('libbpf skeleton test failed')
> + else
> + warning('libbpf skeleton test failed, disabling')
> + endif
> endif
> endif
>
> @@ -2423,6 +2426,14 @@ if have_tools
> dependencies: [authz, crypto, io, qom, qemuutil,
> libcap_ng, mpathpersist],
> install: true)
> +
> + if libbpf.found()
> + executable('qemu-ebpf-rss-helper', files(
> + 'ebpf/qemu-ebpf-rss-helper.c', 'ebpf/ebpf_rss.c'),
> + dependencies: [qemuutil, libbpf, glib],
> + install: true,
> + install_dir: get_option('libexecdir'))
> + endif
> endif
>
> if 'CONFIG_IVSHMEM' in config_host

From:	Andrew Melnichenko
Subject:	Re: [PATCH 4/5] ebpf_rss_helper: Added helper for eBPF RSS.
Date:	Wed, 25 Aug 2021 21:24:41 +0300