[Libguestfs] [PATCH 2/3] p2v: Allow nbdkit as an alternative NBD server to qemu-nbd.

Add code in virt-p2v so that it can use nbdkit (with the file plugin) as an alternative to qemu-nbd. This is controlled through the virt-p2v --nbd command line option, allowing you to select which server (out of qemu-nbd or nbdkit) you prefer (with a fallback). The default is: --nbd=qemu-nbd,nbdkit so qemu-nbd will be used preferentially. --- p2v/conversion.c | 135 ++++++++++++++++++++++++++++++++++++++++++++++--------- p2v/main.c | 92 ++++++++++++++++++++++++++++++++++++- p2v/p2v.h | 9 ++++ p2v/ssh.c | 8 ++-- p2v/virt-p2v.pod | 39 ++++++++++++---- 5 files changed, 248 insertions(+), 35 deletions(-) diff --git a/p2v/conversion.c b/p2v/conversion.c index b25f272..aa9cd4c 100644 --- a/p2v/conversion.c +++ b/p2v/conversion.c @@ -82,8 +82,8 @@ xmlBufferDetach (xmlBufferPtr buf) } #endif -/* How long to wait for qemu-nbd to start (seconds). */ -#define WAIT_QEMU_NBD_TIMEOUT 10 +/* How long to wait for the NBD server to start (seconds). */ +#define WAIT_NBD_TIMEOUT 10 /* Data per NBD connection / physical disk. */ struct data_conn { @@ -93,8 +93,10 @@ struct data_conn { int nbd_remote_port; /* remote NBD port on conversion server */ }; +static pid_t start_nbd (int nbd_local_port, const char *device); static pid_t start_qemu_nbd (int nbd_local_port, const char *device); -static int wait_qemu_nbd (int nbd_local_port, int timeout_seconds); +static pid_t start_nbdkit (int nbd_local_port, const char *device); +static int wait_nbd (int nbd_local_port, int timeout_seconds); static void cleanup_data_conns (struct data_conn *data_conns, size_t nr); static void generate_name (struct config *, const char *filename); static void generate_libvirt_xml (struct config *, struct data_conn *, const char *filename); @@ -240,7 +242,7 @@ start_conversion (struct config *config, data_conns[i].nbd_remote_port = -1; } - /* Start the data connections and qemu-nbd processes, one per disk. */ + /* Start the data connections and NBD server processes, one per disk. */ for (i = 0; config->disks[i] != NULL; ++i) { CLEANUP_FREE char *device = NULL; @@ -284,15 +286,15 @@ start_conversion (struct config *config, data_conns[i].nbd_remote_port, data_conns[i].nbd_local_port); #endif - /* Start qemu-nbd listening on the given port number. */ + /* Start NBD server listening on the given port number. */ data_conns[i].nbd_pid = - start_qemu_nbd (data_conns[i].nbd_local_port, device); + start_nbd (data_conns[i].nbd_local_port, device); if (data_conns[i].nbd_pid == 0) goto out; - /* Wait for qemu-nbd to listen */ - if (wait_qemu_nbd (data_conns[i].nbd_local_port, - WAIT_QEMU_NBD_TIMEOUT) == -1) + /* Wait for NBD server to listen */ + if (wait_nbd (data_conns[i].nbd_local_port, + WAIT_NBD_TIMEOUT) == -1) goto out; } @@ -464,6 +466,42 @@ cancel_conversion (void) } /** + * Start the first server found in the C<nbd_servers> list. + * + * We previously tested all NBD servers (see C<test_nbd_servers>) so + * we only need to run the first server in the list. + * + * Returns the process ID (E<gt> 0) or C<0> if there is an error. + */ +static pid_t +start_nbd (int port, const char *device) +{ + size_t i; + + for (i = 0; i < NR_NBD_SERVERS; ++i) { + switch (nbd_servers[i]) { + case NO_SERVER: + /* ignore */ + break; + + case QEMU_NBD: + return start_qemu_nbd (port, device); + + case NBDKIT: + return start_nbdkit (port, device); + + default: + abort (); + } + } + + /* This should never happen because of the checks in + * test_nbd_servers. + */ + abort (); +} + +/** * Start a local L<qemu-nbd(1)> process. * * Returns the process ID (E<gt> 0) or C<0> if there is an error. @@ -474,6 +512,10 @@ start_qemu_nbd (int port, const char *device) pid_t pid; char port_str[64]; +#if DEBUG_STDERR + fprintf (stderr, "starting qemu-nbd for %s on port %d\n", device, port); +#endif + snprintf (port_str, sizeof port_str, "%d", port); pid = fork (); @@ -504,6 +546,55 @@ start_qemu_nbd (int port, const char *device) return pid; } +/** + * Start a local L<nbdkit(1)> process using the + * L<nbdkit-file-plugin(1)>. + * + * Returns the process ID (E<gt> 0) or C<0> if there is an error. + */ +static pid_t +start_nbdkit (int port, const char *device) +{ + pid_t pid; + char port_str[64]; + CLEANUP_FREE char *file_str = NULL; + +#if DEBUG_STDERR + fprintf (stderr, "starting nbdkit for %s on port %d\n", device, port); +#endif + + snprintf (port_str, sizeof port_str, "%d", port); + + if (asprintf (&file_str, "file=%s", device) == -1) + error (EXIT_FAILURE, errno, "asprintf"); + + pid = fork (); + if (pid == -1) { + set_conversion_error ("fork: %m"); + return 0; + } + + if (pid == 0) { /* Child. */ + close (0); + open ("/dev/null", O_RDONLY); + + execlp ("nbdkit", + "nbdkit", + "-r", /* readonly (vital!) */ + "-p", port_str, /* listening port */ + "-i", "localhost", /* listen only on loopback interface */ + "-f", /* don't fork */ + "file", /* file plugin */ + file_str, /* a device like file=/dev/sda */ + NULL); + perror ("nbdkit"); + _exit (EXIT_FAILURE); + } + + /* Parent. */ + return pid; +} + static int bind_source_port (int sockfd, int family, int source_port); /** @@ -563,7 +654,7 @@ connect_with_source_port (const char *hostname, int dest_port, int source_port) /* Connect. */ if (connect (sockfd, rp->ai_addr, rp->ai_addrlen) == -1) { - set_conversion_error ("waiting for qemu-nbd to start: " + set_conversion_error ("waiting for NBD server to start: " "connect to %s/%s: %m", hostname, dest_port_str); close (sockfd); @@ -606,7 +697,7 @@ bind_source_port (int sockfd, int family, int source_port) goto bound; } - set_conversion_error ("waiting for qemu-nbd to start: " + set_conversion_error ("waiting for NBD server to start: " "bind to source port %d: %m", source_port); freeaddrinfo (results); @@ -618,7 +709,7 @@ bind_source_port (int sockfd, int family, int source_port) } static int -wait_qemu_nbd (int nbd_local_port, int timeout_seconds) +wait_nbd (int nbd_local_port, int timeout_seconds) { int sockfd = -1; int result = -1; @@ -637,12 +728,12 @@ wait_qemu_nbd (int nbd_local_port, int timeout_seconds) if (now_t - start_t >= timeout_seconds) goto cleanup; - /* Source port for probing qemu-nbd should be one greater than - * nbd_local_port. It's not guaranteed to always bind to this port, - * but it will hint the kernel to start there and try incrementally - * higher ports if needed. This avoids the case where the kernel - * selects nbd_local_port as our source port, and we immediately - * connect to ourself. See: + /* Source port for probing NBD server should be one greater than + * nbd_local_port. It's not guaranteed to always bind to this + * port, but it will hint the kernel to start there and try + * incrementally higher ports if needed. This avoids the case + * where the kernel selects nbd_local_port as our source port, and + * we immediately connect to ourself. See: * https://bugzilla.redhat.com/show_bug.cgi?id=1167774#c9 */ sockfd = connect_with_source_port ("localhost", nbd_local_port, @@ -661,7 +752,7 @@ wait_qemu_nbd (int nbd_local_port, int timeout_seconds) recvd = recv (sockfd, magic, sizeof magic - bytes_read, 0); if (recvd == -1) { - set_conversion_error ("waiting for qemu-nbd to start: recv: %m"); + set_conversion_error ("waiting for NBD server to start: recv: %m"); goto cleanup; } @@ -669,8 +760,8 @@ wait_qemu_nbd (int nbd_local_port, int timeout_seconds) } while (bytes_read < sizeof magic); if (memcmp (magic, "NBDMAGIC", sizeof magic) != 0) { - set_conversion_error ("waiting for qemu-nbd to start: " - "'NBDMAGIC' was not received from qemu-nbd"); + set_conversion_error ("waiting for NBD server to start: " + "'NBDMAGIC' was not received from NBD server"); goto cleanup; } @@ -697,7 +788,7 @@ cleanup_data_conns (struct data_conn *data_conns, size_t nr) } if (data_conns[i].nbd_pid > 0) { - /* Kill qemu-nbd process and clean up. */ + /* Kill NBD process and clean up. */ kill (data_conns[i].nbd_pid, SIGTERM); waitpid (data_conns[i].nbd_pid, NULL, 0); } diff --git a/p2v/main.c b/p2v/main.c index 8f8955c..f616b4f 100644 --- a/p2v/main.c +++ b/p2v/main.c @@ -54,7 +54,7 @@ int is_iso_environment = 0; int nbd_local_port; int feature_colours_option = 0; int force_colour = 0; - +enum nbd_server nbd_servers[NR_NBD_SERVERS] = { QEMU_NBD, NBDKIT }; static const char *test_disk = NULL; static void udevadm_settle (void); @@ -62,6 +62,7 @@ static void set_config_defaults (struct config *config); static void find_all_disks (void); static void find_all_interfaces (void); static int cpuinfo_flags (void); +static void test_nbd_servers (void); enum { HELP_OPTION = CHAR_MAX + 1 }; static const char options[] = "Vv"; @@ -73,6 +74,7 @@ static const struct option long_options[] = { { "colour", 0, 0, 0 }, { "colours", 0, 0, 0 }, { "iso", 0, 0, 0 }, + { "nbd", 1, 0, 0 }, { "long-options", 0, 0, 0 }, { "short-options", 0, 0, 0 }, { "test-disk", 1, 0, 0 }, @@ -97,6 +99,7 @@ usage (int status) " --cmdline=CMDLINE Used to debug command line parsing\n" " --colors|--colours Use ANSI colour sequences even if not tty\n" " --iso Running in the ISO environment\n" + " --nbd=qemu-nbd,nbdkit Search order for NBD servers\n" " --test-disk=DISK.IMG For testing, use disk as /dev/sda\n" " -v|--verbose Verbose messages\n" " -V|--version Display version and exit\n" @@ -130,6 +133,35 @@ display_long_options (const struct option *long_options) exit (EXIT_SUCCESS); } +static void +set_nbd_servers (const char *opt) +{ + size_t i; + CLEANUP_FREE_STRING_LIST char **strs + = guestfs_int_split_string (',', opt); + + if (strs == NULL) + error (EXIT_FAILURE, errno, _("malloc")); + + if (strs[0] == NULL) + error (EXIT_FAILURE, 0, _("--nbd option cannot be empty")); + + for (i = 0; strs[i] != NULL; ++i) { + if (i >= NR_NBD_SERVERS) + error (EXIT_FAILURE, 0, _("too many --nbd servers")); + + if (STREQ (strs[i], "qemu-nbd") || STREQ (strs[i], "qemu")) + nbd_servers[i] = QEMU_NBD; + else if (STREQ (strs[i], "nbdkit")) + nbd_servers[i] = NBDKIT; + else + error (EXIT_FAILURE, 0, _("--nbd: unknown server: %s"), strs[i]); + } + + for (; i < NR_NBD_SERVERS; ++i) + nbd_servers[i] = NO_SERVER; +} + int main (int argc, char *argv[]) { @@ -181,6 +213,9 @@ main (int argc, char *argv[]) else if (STREQ (long_options[option_index].name, "iso")) { is_iso_environment = 1; } + else if (STREQ (long_options[option_index].name, "nbd")) { + set_nbd_servers (optarg); + } else if (STREQ (long_options[option_index].name, "test-disk")) { if (test_disk != NULL) error (EXIT_FAILURE, 0, @@ -232,6 +267,8 @@ main (int argc, char *argv[]) /* When testing on the local machine, choose a random port. */ nbd_local_port = 50000 + (random () % 10000); + test_nbd_servers (); + set_config_defaults (config); /* Parse /proc/cmdline (if it exists) or use the --cmdline parameter @@ -272,6 +309,59 @@ udevadm_settle (void) ignore_value (system ("udevadm settle")); } +/* Test the nbd_servers[] array to see which servers are actually + * installed and appear to be working. If a server is not installed + * we set the corresponding nbd_servers[i] = NO_SERVER. + */ +static void +test_nbd_servers (void) +{ + size_t i; + int r; + + for (i = 0; i < NR_NBD_SERVERS; ++i) { + switch (nbd_servers[i]) { + case NO_SERVER: + /* ignore entry */ + break; + + case QEMU_NBD: + r = system ("qemu-nbd --version" +#ifndef DEBUG_STDERR + " >/dev/null 2>&1" +#endif + ); + if (r != 0) + nbd_servers[i] = NO_SERVER; + break; + + case NBDKIT: + r = system ("nbdkit file --version" +#ifndef DEBUG_STDERR + " >/dev/null 2>&1" +#endif + ); + if (r != 0) + nbd_servers[i] = NO_SERVER; + break; + + default: + abort (); + } + } + + for (i = 0; i < NR_NBD_SERVERS; ++i) + if (nbd_servers[i] != NO_SERVER) + return; + + /* If we reach here, there are no servers left, so we have to exit. */ + fprintf (stderr, + _("%s: no working NBD server was found, cannot continue.\n" + "Please check the --nbd option in the virt-p2v(1) man page.\n"), + getprogname ()); + exit (EXIT_FAILURE); +} + static void set_config_defaults (struct config *config) { diff --git a/p2v/p2v.h b/p2v/p2v.h index df23898..d805aaf 100644 --- a/p2v/p2v.h +++ b/p2v/p2v.h @@ -63,6 +63,15 @@ extern int feature_colours_option; /* virt-p2v --colours option (used by ansi_* macros). */ extern int force_colour; +/* virt-p2v --nbd option. */ +enum nbd_server { + NO_SERVER = 0, + QEMU_NBD = 1, + NBDKIT = 2, +#define NR_NBD_SERVERS 2 +}; +extern enum nbd_server nbd_servers[NR_NBD_SERVERS]; + /* config.c */ struct config { char *server; diff --git a/p2v/ssh.c b/p2v/ssh.c index 74ae126..4c1d64c 100644 --- a/p2v/ssh.c +++ b/p2v/ssh.c @@ -31,10 +31,10 @@ * Once we start conversion, we will open a control connection to send * the libvirt configuration data and to start up virt-v2v, and we * will open up one data connection per local hard disk. The data - * connection(s) have a reverse port forward to the local - * L<qemu-nbd(8)> server which is serving the content of that hard - * disk. The remote port for each data connection is assigned by ssh. - * See C<open_data_connection> and C<start_remote_conversion>. + * connection(s) have a reverse port forward to the local NBD server + * which is serving the content of that hard disk. The remote port + * for each data connection is assigned by ssh. See + * C<open_data_connection> and C<start_remote_conversion>. */ #include <config.h> diff --git a/p2v/virt-p2v.pod b/p2v/virt-p2v.pod index ec8eff2..e04c1f1 100644 --- a/p2v/virt-p2v.pod +++ b/p2v/virt-p2v.pod @@ -597,6 +597,24 @@ virt-p2v ISO environment, ie. when it is running on a real physical machine (and thus not when testing). It enables various dangerous features such as the Reboot button. +=item B<--nbd=server[,server...]> + +Select which NBD server is used. By default the following +servers are checked and the first one found is used: +I<--nbd=qemu-nbd,nbdkit> + +=over 4 + +=item B<qemu-nbd> + +Use qemu-nbd. + +=item B<nbdkit> + +Use nbdkit with the file plugin (see: L<nbdkit-file-plugin(1)>). + +=back + =item B<--test-disk=/PATH/TO/DISK.IMG> For testing or debugging purposes, replace F</dev/sda> with a local @@ -731,11 +749,15 @@ interest only, do not attempt to run this script yourself. =back Before conversion actually begins, virt-p2v then makes one or more -further ssh connections to the server for data transfer. The transfer -protocol used currently is NBD (Network Block Device), which is -proxied over ssh. The server is L<qemu-nbd(1)>. There is one ssh -connection per physical hard disk on the source machine (the common -case — a single hard disk — is shown below): +further ssh connections to the server for data transfer. + +The transfer protocol used currently is NBD (Network Block Device), +which is proxied over ssh. The NBD server is L<qemu-nbd(1)> by +default but others can be selected using the I<--nbd> command line +option. + +There is one ssh connection per physical hard disk on the source +machine (the common case — a single hard disk — is shown below): ┌──────────────┐ ┌─────────────────┐ │ virt-p2v │ │ virt-v2v │ @@ -754,9 +776,9 @@ server and terminates on the conversion server, in fact NBD requests flow in the opposite direction. This is because the reverse port forward feature of ssh (C<ssh -R>) is used to open a port on the loopback interface of the conversion server which is proxied back by -ssh to the qemu-nbd server running on the physical machine. The -effect is that virt-v2v via libguestfs can open nbd connections which -directly read the hard disk(s) of the physical server. +ssh to the NBD server running on the physical machine. The effect is +that virt-v2v via libguestfs can open nbd connections which directly +read the hard disk(s) of the physical server. Two layers of protection are used to ensure that there are no writes to the hard disks: Firstly, the qemu-nbd I<-r> (readonly) option is @@ -783,6 +805,7 @@ L<virt-p2v-make-kickstart(1)>, L<virt-p2v-make-kiwi(1)>, L<virt-v2v(1)>, L<qemu-nbd(1)>, +L<nbdkit(1)>, L<nbdkit-file-plugin(1)>, L<ssh(1)>, L<sshd(8)>, L<sshd_config(5)>, -- 2.9.3