Previously, attempts to use nbdkit without -r in order to visit a read-only image failed to open the image (in fact, a single read-only file in an otherwise usable directory makes "nbdkit file dir=. --run 'nbdinfo --list'" fail to print anything in libnbd 1.6). But a saner approach is to try a fallback to a readonly fd if a read-write fd fails. The windows code compiles, but I wasn't able to test it as thoroughly as the Unix code. --- plugins/file/file.c | 30 ++++++++++++++++-- plugins/file/winfile.c | 21 +++++++++++-- tests/Makefile.am | 12 +++++-- tests/test-file-readonly.sh | 63 +++++++++++++++++++++++++++++++++++++ 4 files changed, 118 insertions(+), 8 deletions(-) create mode 100755 tests/test-file-readonly.sh diff --git a/plugins/file/file.c b/plugins/file/file.c index 1651079a..a9ecceb6 100644 --- a/plugins/file/file.c +++ b/plugins/file/file.c @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2020 Red Hat Inc. + * Copyright (C) 2013-2021 Red Hat Inc. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are @@ -304,6 +304,7 @@ struct handle { int fd; bool is_block_device; int sector_size; + bool can_write; bool can_punch_hole; bool can_zero_range; bool can_fallocate; @@ -343,12 +344,25 @@ file_open (int readonly) } flags = O_CLOEXEC|O_NOCTTY; - if (readonly) + if (readonly) { flags |= O_RDONLY; - else + h->can_write = false; + } + else { flags |= O_RDWR; + h->can_write = true; + } h->fd = openat (dfd, file, flags); + if (h->fd == -1 && !readonly) { + int saved_errno = errno; + flags = (flags & ~O_ACCMODE) | O_RDONLY; + h->fd = openat (dfd, file, flags); + if (h->fd == -1) + errno = saved_errno; + else + h->can_write = false; + } if (h->fd == -1) { nbdkit_error ("open: %s: %m", file); if (dfd != -1) @@ -464,6 +478,15 @@ file_get_size (void *handle) } } +/* Check if file is read-only. */ +static int +file_can_write (void *handle) +{ + struct handle *h = handle; + + return h->can_write; +} + /* Allow multiple parallel connections from a single client. */ static int file_can_multi_conn (void *handle) @@ -880,6 +903,7 @@ static struct nbdkit_plugin plugin = { .open = file_open, .close = file_close, .get_size = file_get_size, + .can_write = file_can_write, .can_multi_conn = file_can_multi_conn, .can_trim = file_can_trim, .can_fua = file_can_fua, diff --git a/plugins/file/winfile.c b/plugins/file/winfile.c index 6d1a6643..ec186255 100644 --- a/plugins/file/winfile.c +++ b/plugins/file/winfile.c @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2020 Red Hat Inc. + * Copyright (C) 2013-2021 Red Hat Inc. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are @@ -106,6 +106,7 @@ winfile_dump_plugin (void) struct handle { HANDLE fh; int64_t size; + bool is_readonly; bool is_volume; bool is_sparse; }; @@ -126,6 +127,12 @@ winfile_open (int readonly) fh = CreateFile (filename, flags, FILE_SHARE_READ|FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); + if (fh == INVALID_HANDLE_VALUE && !readonly) { + flags &= ~GENERIC_WRITE; + readonly = true; + fh = CreateFile (filename, flags, FILE_SHARE_READ|FILE_SHARE_WRITE, + NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); + } if (fh == INVALID_HANDLE_VALUE) { nbdkit_error ("%s: error %lu", filename, GetLastError ()); return NULL; @@ -179,15 +186,24 @@ winfile_open (int readonly) } h->fh = fh; h->size = size.QuadPart; + h->is_readonly = readonly; h->is_volume = is_volume; h->is_sparse = is_sparse; - nbdkit_debug ("%s: size=%" PRIi64 " is_volume=%s is_sparse=%s", + nbdkit_debug ("%s: size=%" PRIi64 " readonly=%s is_volume=%s is_sparse=%s", filename, h->size, + readonly ? "true" : "false", is_volume ? "true" : "false", is_sparse ? "true" : "false"); return h; } +static int +wintfile_can_write (void *handle) +{ + struct handle *h = handle; + return !h->is_readonly; +} + static int winfile_can_trim (void *handle) { @@ -425,6 +441,7 @@ static struct nbdkit_plugin plugin = { .dump_plugin = winfile_dump_plugin, .open = winfile_open, + .can_write = winfile_can_write, .can_trim = winfile_can_trim, .can_zero = winfile_can_zero, .can_extents = winfile_can_extents, diff --git a/tests/Makefile.am b/tests/Makefile.am index 70898f20..e8c9c535 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -1,5 +1,5 @@ # nbdkit -# Copyright (C) 2013-2020 Red Hat Inc. +# Copyright (C) 2013-2021 Red Hat Inc. # # Redistribution and use in source and binary forms, with or without # modification, are permitted provided that the following conditions are @@ -673,8 +673,14 @@ EXTRA_DIST += \ $(NULL) # file plugin test. -TESTS += test-file.sh -EXTRA_DIST += test-file.sh +TESTS += \ + test-file.sh \ + test-file-readonly.sh \ + $(NULL) +EXTRA_DIST += \ + test-file.sh \ + test-file-readonly.sh \ + $(NULL) LIBGUESTFS_TESTS += test-file-block test_file_block_SOURCES = test-file-block.c test.h diff --git a/tests/test-file-readonly.sh b/tests/test-file-readonly.sh new file mode 100755 index 00000000..cde2bd65 --- /dev/null +++ b/tests/test-file-readonly.sh @@ -0,0 +1,63 @@ +#!/usr/bin/env bash +# nbdkit +# Copyright (C) 2013-2021 Red Hat Inc. +# +# Redistribution and use in source and binary forms, with or without +# modification, are permitted provided that the following conditions are +# met: +# +# * Redistributions of source code must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# +# * Redistributions in binary form must reproduce the above copyright +# notice, this list of conditions and the following disclaimer in the +# documentation and/or other materials provided with the distribution. +# +# * Neither the name of Red Hat nor the names of its contributors may be +# used to endorse or promote products derived from this software without +# specific prior written permission. +# +# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND +# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, +# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A +# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR +# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF +# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, +# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT +# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +# SUCH DAMAGE. + +# Test the file plugin on readonly files. + +source ./functions.sh +set -e +set -x + +requires_plugin file +requires_nbdsh_uri +requires truncate --version + +sock=$(mktemp -u /tmp/nbdkit-test-sock.XXXXXX) +files="file-readonly.pid file-readonly.img $sock" +rm -f $files +cleanup_fn rm -f $files + +truncate -s 16384 file-readonly.img +chmod a-w file-readonly.img +start_nbdkit -P file-readonly.pid -U $sock file file-readonly.img + +# Try to test all the major functions supported by both +# the Unix and Windows versions of the file plugin. +nbdsh -u "nbd+unix://?socket=$sock" -c ' +assert h.is_read_only() +assert not h.can_zero() + +buf = h.pread(8192, 0) +assert buf == b"\0" * 8192 + +if h.can_flush(): + h.flush() +' -- 2.30.1