On 7/13/23 19:10, Laszlo Ersek wrote:
> On QEMU 7.2.0+, if "passt" is available, ask QEMU for passt ("stream")
> rather than SLIRP ("user") networking.
>
> For this, we need to run passt ourselves. Given that passt daemonizes by
> default, start it with our traditional function guestfs_int_cmd_run(). Ask
> passt to save its PID file, because in case something goes wrong before
> we're completely sure the appliance (i.e. QEMU) is up and running, we'll
> need to kill passt, the *grandchild*, ourselves.
>
> Pass "--one-off" to passt (same as libvirt). This way, once we have proof
> that QEMU has connected to passt (because the appliance shows signs of
> life), we need not clean up passt ourselves -- once QEMU exits, passt will
> see an EOF on the unix domain socket, and exit as well.
>
> Passt is way more flexible than SLIRP, and passt normally intends to
> imitate the host environment in the guest as much as possible. This means
> that, when switching from SLIRP to passt, the guest would see changes to
> the following:
>
> - guest IP address,
>
> - guest subnet mask,
>
> - host (= gateway) IP address,
>
> - host (= gateway) MAC address.
>
> Extract the SLIRP defaults into the new macros NETWORK_GW_IP and
> NETWORK_GW_MAC, and pass them explicitly to passt. In particular,
> "tests/rsync/test-rsync.sh" fails without setting the host address
> (NETWORK_GW_IP) properly.
>
> (These artifacts can be verified in the appliance with "virt-rescue
> --network", by running "ip addr", "ip route", and "ip neighbor" at the
> virt-rescue prompt. There are four scenarios: two libguest backends, times
> passt being installed or not installed.)
>
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2184967
> Signed-off-by: Laszlo Ersek <ler...@redhat.com>
> ---
> lib/guestfs-internal.h | 26 ++++
> lib/launch-direct.c | 147 +++++++++++++++++++-
> 2 files changed, 168 insertions(+), 5 deletions(-)
>
> diff --git a/lib/guestfs-internal.h b/lib/guestfs-internal.h
> index 9ba4d4ad46cf..9f4f800e6d6e 100644
> --- a/lib/guestfs-internal.h
> +++ b/lib/guestfs-internal.h
> @@ -158,6 +158,32 @@ cleanup_mutex_unlock (pthread_mutex_t **ptr)
> #define NETWORK_ADDRESS "169.254.2.15"
> #define NETWORK_PREFIX "16"
>
> +/* The IP address and the MAC address of the host, as seen from the
> appliance.
> + *
> + * NETWORK_GW_IP should be the same as NETWORK_ADDRESS, only replacing ".15"
> in
> + * the rightmost octet with ".2". NETWORK_GW_MAC cannot be changed. These
> + * restrictions are a consequence of the following landscape:
> + *
> + * libguestfs backend userspace network stack restrictions
> + * ------------------ -----------------------
> --------------------------------
> + * direct passt None; both NETWORK_GW_IP and
> + * NETWORK_GW_MAC can be set on
> the
> + * passt command line.
> + *
> + * direct SLIRP SLIRP hard-codes
> NETWORK_GW_MAC.
> + *
> + * libvirt passt The domain XML does not
> expose
> + * either knob (RHBZ#2222766),
> even
> + * though passt could accept
> both.
> + *
> + * libvirt SLIRP The domain XML does not
> expose
> + * either knob (RHBZ#2222766),
> and
> + * SLIRP hard-codes
> NETWORK_GW_MAC
> + * anyway.
> + */
> +#define NETWORK_GW_IP "169.254.2.2"
> +#define NETWORK_GW_MAC "52:56:00:00:00:02"
> +
> /* Guestfs handle and associated structures. */
>
> /* State. */
> diff --git a/lib/launch-direct.c b/lib/launch-direct.c
> index 3f46f0509736..8d6ad025a4e1 100644
> --- a/lib/launch-direct.c
> +++ b/lib/launch-direct.c
> @@ -32,6 +32,7 @@
> #include <errno.h>
> #include <fcntl.h>
> #include <sys/types.h>
> +#include <sys/wait.h>
> #include <sys/time.h>
> #include <sys/resource.h>
> #include <sys/stat.h>
> @@ -48,6 +49,7 @@
> #include "guestfs-internal.h"
> #include "guestfs_protocol.h"
> #include "qemuopts.h"
> +#include "ignore-value.h"
>
> /* Per-handle data. */
> struct backend_direct_data {
> @@ -333,6 +335,110 @@ add_drives (guestfs_h *g, struct backend_direct_data
> *data,
> return 0;
> }
>
> +/**
> + * Launch passt such that it daemonizes.
> + *
> + * On error, -1 is returned; C<passt_pid> and C<sockpath> are not modified.
> + *
> + * On success, 0 is returned. C<passt_pid> contains the PID of the passt
> + * background process. C<sockpath> contains the pathname of the unix domain
> + * socket where passt will accept a single connection.
> + */
Arguably, I should have typed C<-1> and C<0> above; I can fix those up,
upon pushing, in case no more changes were requested.
Laszlo
> +static int
> +launch_passt (guestfs_h *g, long *passt_pid, char (*sockpath)[UNIX_PATH_MAX])
> +{
> + int rc;
> + char sockpath_local[sizeof *sockpath];
> + char *pid_path;
> + struct command *cmd;
> + int passt_status;
> + int passt_exit;
> + char *pid_str;
> + long passt_pid_local;
> + char *endptr;
> +
> + rc = -1;
> + if (guestfs_int_create_socketname (g, "passt.sock", &sockpath_local) == -1)
> + return rc;
> +
> + pid_path = guestfs_int_make_pid_path (g, "passt");
> + if (pid_path == NULL)
> + return rc;
> +
> + cmd = guestfs_int_new_command (g);
> + if (cmd == NULL)
> + goto free_pid_path;
> +
> + guestfs_int_cmd_add_arg (cmd, "passt");
> + guestfs_int_cmd_add_arg (cmd, "--one-off");
> + guestfs_int_cmd_add_arg (cmd, "--socket");
> + guestfs_int_cmd_add_arg (cmd, sockpath_local);
> + guestfs_int_cmd_add_arg (cmd, "--pid");
> + guestfs_int_cmd_add_arg (cmd, pid_path);
> + guestfs_int_cmd_add_arg (cmd, "--address");
> + guestfs_int_cmd_add_arg (cmd, NETWORK_ADDRESS);
> + guestfs_int_cmd_add_arg (cmd, "--netmask");
> + guestfs_int_cmd_add_arg (cmd, NETWORK_PREFIX);
> + guestfs_int_cmd_add_arg (cmd, "--mac-addr");
> + guestfs_int_cmd_add_arg (cmd, NETWORK_GW_MAC);
> + guestfs_int_cmd_add_arg (cmd, "--gateway");
> + guestfs_int_cmd_add_arg (cmd, NETWORK_GW_IP);
> +
> + passt_status = guestfs_int_cmd_run (cmd);
> + if (passt_status == -1)
> + /* guestfs_int_cmd_run() reports errors internally, so just bail here */
> + goto close_cmd;
> +
> + if (WIFSIGNALED (passt_status)) {
> + error (g, _("passt was killed with signal %d"), WTERMSIG (passt_status));
> + goto close_cmd;
> + }
> +
> + assert (WIFEXITED (passt_status));
> + passt_exit = WEXITSTATUS (passt_status);
> + if (passt_exit != 0) {
> + error (g, _("passt exited with status %d"), passt_exit);
> + goto close_cmd;
> + }
> +
> + /* At this point passt has forked into the background, dropped privileges,
> and
> + * written a PID file. Due to "--one-off", passt will exit once our QEMU
> + * appliance disappears (forcibly or cleanly); however, we still need the
> + * passt PID *temporarily*, so we can kill passt in case we encounter an
> error
> + * *before* starting the appliance.
> + */
> + if (guestfs_int_read_whole_file (g, pid_path, &pid_str, NULL) == -1)
> + /* Any error has been reported internally, so just bail. We can't kill
> + * passt here because we've failed to get its PID in the first place...
> + */
> + goto close_cmd;
> +
> + errno = 0;
> + passt_pid_local = strtol (pid_str, &endptr, 10);
> + if (endptr == pid_str || (*endptr != '\0' && *endptr != '\n') || errno !=
> 0 ||
> + passt_pid_local <= 1) {
> + /* Same thing, we can't kill passt just yet. */
> + error (g, _("failed to parse passt PID from '%s'"), pid_path);
> + goto free_pid_str;
> + }
> +
> + /* We're done. */
> + *passt_pid = passt_pid_local;
> + ignore_value (strcpy (*sockpath, sockpath_local));
> + rc = 0;
> +
> +free_pid_str:
> + free (pid_str);
> +
> +close_cmd:
> + guestfs_int_cmd_close (cmd);
> +
> +free_pid_path:
> + free (pid_path);
> +
> + return rc;
> +}
> +
> static int
> launch_direct (guestfs_h *g, void *datav, const char *arg)
> {
> @@ -340,6 +446,7 @@ launch_direct (guestfs_h *g, void *datav, const char *arg)
> struct qemuopts *qopts = NULL;
> int daemon_accept_sock = -1, console_sock = -1;
> int r;
> + long passt_pid = -1;
> int flags;
> int sv[2];
> struct sockaddr_un addr;
> @@ -658,11 +765,30 @@ launch_direct (guestfs_h *g, void *datav, const char
> *arg)
>
> /* Enable user networking. */
> if (g->enable_network) {
> - start_list ("-netdev") {
> - append_list ("user");
> - append_list ("id=usernet");
> - append_list ("net=" NETWORK_ADDRESS "/" NETWORK_PREFIX);
> - } end_list ();
> + /* If qemu is 7.2.0+ and "passt" is available, ask for passt rather
> + * than SLIRP. RHBZ#2184967.
> + */
> + if (guestfs_int_version_ge (&data->qemu_version, 7, 2, 0) &&
> + guestfs_int_passt_runnable (g)) {
> + char passt_sock[UNIX_PATH_MAX];
> +
> + if (launch_passt (g, &passt_pid, &passt_sock) == -1)
> + goto cleanup0;
> +
> + start_list ("-netdev") {
> + append_list ("stream");
> + append_list ("id=usernet");
> + append_list ("addr.type=unix");
> + append_list_format ("addr.path=%s", passt_sock);
> + } end_list ();
> + }
> + else {
> + start_list ("-netdev") {
> + append_list ("user");
> + append_list ("id=usernet");
> + append_list ("net=" NETWORK_ADDRESS "/" NETWORK_PREFIX);
> + } end_list ();
> + }
> start_list ("-device") {
> append_list (VIRTIO_DEVICE_NAME ("virtio-net"));
> append_list ("netdev=usernet");
> @@ -893,6 +1019,15 @@ launch_direct (guestfs_h *g, void *datav, const char
> *arg)
>
> debug (g, "appliance is up");
>
> + /* From this point onward, even if we fail, QEMU terminating (forcefully or
> + * gracefully) will cause passt to go away as well. Note that we can't
> + * precisely tell whether QEMU managed to open the passt socket before QEMU
> + * failed. Therefore, err on the side of killing passt needlessly, rather
> + * than not killing it when needed -- that's why we re-set "passt_pid" to
> (-1)
> + * only this late during QEMU startup verification.
> + */
> + passt_pid = -1;
> +
> /* This is possible in some really strange situations, such as
> * guestfsd starts up OK but then qemu immediately exits. Check for
> * it because the caller is probably expecting to be able to send
> @@ -924,6 +1059,8 @@ launch_direct (guestfs_h *g, void *datav, const char
> *arg)
> data->qemu_data = NULL;
>
> cleanup0:
> + if (passt_pid != -1)
> + kill (passt_pid, SIGTERM);
> if (qopts != NULL)
> qemuopts_free (qopts);
> if (daemon_accept_sock >= 0)
> _______________________________________________
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>
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