[RFC PATCH 3/5] ebpf_rss_helper: Added helper for eBPF RSS.

[Andrew Melnychenko <andrew@daynix.com>]

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.

Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
---
 ebpf/qemu-ebpf-rss-helper.c | 130 ++++++++++++++++++++++++++++++++++++
 meson.build                 |   8 +++
 2 files changed, 138 insertions(+)
 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..f0379dddf2
--- /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"
+
+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);
+    }
+
+    fprintf(stderr, "FD %s\n", fd_string);
+
+    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;
+    fds[2] = ctx.map_toeplitz_key;
+    fds[3] = ctx.map_indirections_table;
+
+    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 626cf932c1..ce26bddead 100644
--- a/meson.build
+++ b/meson.build
@@ -2413,6 +2413,14 @@ 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
-- 
2.31.1