Hi, > I wonder if this can be done as helper for TAP/bridge. > Well, it does already, libvirt may create TAP device and pass it in command line or using getfd qmp command.
E.g it's the qemu to launch those helper with set-uid. > Then libvirt won't even need to care about that? Yea, we may think about this routine in the future as a fallback. Do we need to test whether the bpf can do mmap() here? > I'm not sure that it's required. On Fri, Aug 20, 2021 at 6:41 AM Jason Wang <jasow...@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 <and...@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 <and...@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 > >
