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Re: [PATCH] support: Implement <support/descriptors.h> to track file descriptors
- From: Carlos O'Donell <carlos at redhat dot com>
- To: Florian Weimer <fweimer at redhat dot com>, libc-alpha at sourceware dot org
- Date: Thu, 29 Nov 2018 22:44:10 -0500
- Subject: Re: [PATCH] support: Implement <support/descriptors.h> to track file descriptors
- References: <875zwifn4p.fsf@oldenburg.str.redhat.com>
On 11/27/18 12:25 PM, Florian Weimer wrote:
> 2018-11-27 Florian Weimer <fweimer@redhat.com>
>
> * support/descriptors.h: New file.
> * support/check.h (support_record_failure_is_failed): Declare.
> * support/support_descriptors.c: Likewise.
> * support/tst-support_descriptors.c: Likewise.
> * support/support_record_faile.c
> (support_record_failure_is_failed): New function.
> * support/Makefile (libsupport-routines): Add support_descriptors.
> (tests): Add tst-support_descriptors.
I was wondering how you were going to implement this :-)
Two comments below.
OK to commit to master if you resolve those two comments.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> diff --git a/support/Makefile b/support/Makefile
> index a2536980d1..93a5143016 100644
> --- a/support/Makefile
> +++ b/support/Makefile
> @@ -46,6 +46,7 @@ libsupport-routines = \
> support_chroot \
> support_copy_file_range \
> support_descriptor_supports_holes \
> + support_descriptors \
OK.
> support_enter_mount_namespace \
> support_enter_network_namespace \
> support_format_address_family \
> @@ -195,6 +196,7 @@ tests = \
> tst-support-namespace \
> tst-support_blob_repeat \
> tst-support_capture_subprocess \
> + tst-support_descriptors \
OK.
> tst-support_format_dns_packet \
> tst-support_quote_blob \
> tst-support_quote_string \
> diff --git a/support/check.h b/support/check.h
> index e6765289f2..7ea9a86a9c 100644
> --- a/support/check.h
> +++ b/support/check.h
> @@ -183,6 +183,10 @@ int support_report_failure (int status)
> /* Internal function used to test the failure recording framework. */
> void support_record_failure_reset (void);
>
> +/* Returns true or false depending on whether there have been test
> + failures or not. */
> +int support_record_failure_is_failed (void);
OK.
> +
> __END_DECLS
>
> #endif /* SUPPORT_CHECK_H */
> diff --git a/support/descriptors.h b/support/descriptors.h
> new file mode 100644
> index 0000000000..8ec4cbbdfb
> --- /dev/null
> +++ b/support/descriptors.h
> @@ -0,0 +1,47 @@
> +/* Monitoring file descriptor usage.
> + Copyright (C) 2018 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <http://www.gnu.org/licenses/>. */
> +
> +#ifndef SUPPORT_DESCRIPTORS_H
> +#define SUPPORT_DESCRIPTORS_H
> +
> +#include <stdio.h>
> +
> +/* Opaque pointer, for capturing file descriptor lists. */
> +struct support_descriptors;
> +
> +/* Record the currently open file descriptors and store them in the
> + returned list. Terminate the process if the listing operation
> + fails. */
> +struct support_descriptors *support_descriptors_list (void);
> +
> +/* Deallocate the list of descriptors. */
> +void support_descriptors_free (struct support_descriptors *);
> +
> +/* Write the list of descriptors to STREAM, adding PREFIX to each
> + line. */
> +void support_descriptors_dump (struct support_descriptors *,
> + const char *prefix, FILE *stream);
> +
> +/* Check for file descriptor leaks and other file descriptor changes:
> + Compare the current list of descriptors with the passed list.
> + Record a test failure if there are additional open descriptors,
> + descriptors have been closed, or if a change in file descriptor can
> + be detected. */
> +void support_descriptors_check (struct support_descriptors *);
> +
> +#endif /* SUPPORT_DESCRIPTORS_H */
> diff --git a/support/support_descriptors.c b/support/support_descriptors.c
> new file mode 100644
> index 0000000000..99ca566802
> --- /dev/null
> +++ b/support/support_descriptors.c
> @@ -0,0 +1,265 @@
> +/* Monitoring file descriptor usage.
> + Copyright (C) 2018 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <http://www.gnu.org/licenses/>. */
> +
> +#include <dirent.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <support/check.h>
> +#include <support/support.h>
> +#include <sys/stat.h>
> +#include <sys/sysmacros.h>
> +#include <xunistd.h>
> +
> +struct descriptor
> +{
> + int fd;
> + char *link_target;
> + dev_t dev;
> + ino64_t ino;
> +};
OK.
> +
> +/* Used with qsort. */
> +static int
> +descriptor_compare (const void *l, const void *r)
> +{
> + const struct descriptor *left = l;
> + const struct descriptor *right = r;
> + /* Cannot overflow due to limited file descriptor range. */
> + return left->fd - right->fd;
> +}
> +
> +#define DYNARRAY_STRUCT descriptor_list
> +#define DYNARRAY_ELEMENT struct descriptor
> +#define DYNARRAY_PREFIX descriptor_list_
> +#define DYNARRAY_ELEMENT_FREE(e) free ((e)->link_target)
> +#define DYNARRAY_INITIAL_SIZE 0
> +#include <malloc/dynarray-skeleton.c>
> +
> +struct support_descriptors
> +{
> + struct descriptor_list list;
> +};
> +
> +struct support_descriptors *
> +support_descriptors_list (void)
> +{
> + struct support_descriptors *result = xmalloc (sizeof (*result));
> + descriptor_list_init (&result->list);
> +
> + DIR *fds = opendir ("/proc/self/fd");
This makes support/descriptors.h dependent on /proc/self/fd?
Can we exit UNSUPPORTED if it doesn't exist?
> + if (fds == NULL)
> + FAIL_EXIT1 ("opendir (\"/proc/self/fd\"): %m");
> +
> + while (true)
> + {
> + errno = 0;
> + struct dirent64 *e = readdir64 (fds);
> + if (e == NULL)
> + {
> + if (errno != 0)
> + FAIL_EXIT1 ("readdir: %m");
> + break;
> + }
> +
> + if (e->d_name[0] == '.')
> + continue;
> +
> + char *endptr;
> + long fd = strtol (e->d_name, &endptr, 10);
> + if (*endptr != '\0' || fd < 0 || fd > INT_MAX)
> + FAIL_EXIT1 ("readdir: invalid file descriptor name: /proc/self/fd/%s",
> + e->d_name);
> +
> + /* Skip the descriptor which is used to enumerate the
> + descriptors. */
> + if (fd == dirfd (fds))
> + continue;
> +
> + char path[100];
Why not PATH_MAX?
We should not stat a truncated fd path since it might match another fd?
assert (strlen(e->d_name) < PATH_MAX);
> + snprintf (path, sizeof (path), "/proc/self/fd/%ld", fd);
> + char *target = xreadlink (path);
> + struct stat64 st;
> + if (fstat64 (fd, &st) != 0)
> + FAIL_EXIT1 ("readdir: fstat64 (%ld) failed: %m", fd);
> +
> + struct descriptor *item = descriptor_list_emplace (&result->list);
> + if (item == NULL)
> + FAIL_EXIT1 ("descriptor_list_emplace: %m");
> + item->fd = fd;
> + item->link_target = target;
> + item->dev = st.st_dev;
> + item->ino = st.st_ino;
> + }
> +
> + closedir (fds);
> +
> + qsort (descriptor_list_begin (&result->list),
> + descriptor_list_size (&result->list),
> + sizeof (struct descriptor), descriptor_compare);
> +
> + return result;
> +}
> +
> +void
> +support_descriptors_free (struct support_descriptors *descrs)
> +{
> + descriptor_list_free (&descrs->list);
> + free (descrs);
> +}
> +
> +void
> +support_descriptors_dump (struct support_descriptors *descrs,
> + const char *prefix, FILE *fp)
> +{
> + struct descriptor *end = descriptor_list_end (&descrs->list);
> + for (struct descriptor *d = descriptor_list_begin (&descrs->list);
> + d != end; ++d)
> + {
> + char *quoted = support_quote_string (d->link_target);
> + fprintf (fp, "%s%d: target=\"%s\" major=%lld minor=%lld ino=%lld\n",
> + prefix, d->fd, quoted,
> + (long long int) major (d->dev),
> + (long long int) minor (d->dev),
> + (long long int) d->ino);
> + free (quoted);
> + }
> +}
> +
> +static void
> +dump_mismatch (bool *first,
> + struct support_descriptors *descrs,
> + struct support_descriptors *current)
> +{
> + if (*first)
> + *first = false;
> + else
> + return;
> +
> + puts ("error: Differences found in descriptor set");
> + puts ("Reference descriptor set:");
> + support_descriptors_dump (descrs, " ", stdout);
> + puts ("Current descriptor set:");
> + support_descriptors_dump (current, " ", stdout);
> + puts ("Differences:");
> +}
> +
> +static void
> +report_closed_descriptor (bool *first,
> + struct support_descriptors *descrs,
> + struct support_descriptors *current,
> + struct descriptor *left)
> +{
> + support_record_failure ();
> + dump_mismatch (first, descrs, current);
> + printf ("error: descriptor %d was closed\n", left->fd);
> +}
> +
> +static void
> +report_opened_descriptor (bool *first,
> + struct support_descriptors *descrs,
> + struct support_descriptors *current,
> + struct descriptor *right)
> +{
> + support_record_failure ();
> + dump_mismatch (first, descrs, current);
> + char *quoted = support_quote_string (right->link_target);
> + printf ("error: descriptor %d was opened (\"%s\")\n", right->fd, quoted);
> + free (quoted);
> +}
> +
> +void
> +support_descriptors_check (struct support_descriptors *descrs)
> +{
> + struct support_descriptors *current = support_descriptors_list ();
> +
> + struct descriptor *left = descriptor_list_begin (&descrs->list);
> + struct descriptor *left_end = descriptor_list_end (&descrs->list);
> + struct descriptor *right = descriptor_list_begin (¤t->list);
> + struct descriptor *right_end = descriptor_list_end (¤t->list);
> +
> + bool first = true;
> + while (left != left_end && right != right_end)
> + {
> + if (left->fd == right->fd)
> + {
> + if (strcmp (left->link_target, right->link_target) != 0)
> + {
> + support_record_failure ();
> + char *left_quoted = support_quote_string (left->link_target);
> + char *right_quoted = support_quote_string (right->link_target);
> + dump_mismatch (&first, descrs, current);
> + printf ("error: descriptor %d changed from \"%s\" to \"%s\"\n",
> + left->fd, left_quoted, right_quoted);
> + free (left_quoted);
> + free (right_quoted);
> + }
> + if (left->dev != right->dev)
> + {
> + support_record_failure ();
> + dump_mismatch (&first, descrs, current);
> + printf ("error: descriptor %d changed device"
> + " from %lld:%lld to %lld:%lld\n",
> + left->fd,
> + (long long int) major (left->dev),
> + (long long int) minor (left->dev),
> + (long long int) major (right->dev),
> + (long long int) minor (right->dev));
> + }
> + if (left->ino != right->ino)
> + {
> + support_record_failure ();
> + dump_mismatch (&first, descrs, current);
> + printf ("error: descriptor %d changed ino from %lld to %lld\n",
> + left->fd,
> + (long long int) left->ino, (long long int) right->ino);
> + }
> + ++left;
> + ++right;
> + }
> + else if (left->fd < right->fd)
> + {
> + /* Gap on the right. */
> + report_closed_descriptor (&first, descrs, current, left);
> + ++left;
> + }
> + else
> + {
> + /* Gap on the left. */
> + TEST_VERIFY_EXIT (left->fd > right->fd);
> + report_opened_descriptor (&first, descrs, current, right);
> + ++right;
> + }
> + }
> +
> + while (left != left_end)
> + {
> + /* Closed descriptors (more descriptors on the left). */
> + report_closed_descriptor (&first, descrs, current, left);
> + ++left;
> + }
> +
> + while (right != right_end)
> + {
> + /* Opened descriptors (more descriptors on the right). */
> + report_opened_descriptor (&first, descrs, current, right);
> + ++right;
> + }
> +
> + support_descriptors_free (current);
> +}
OK.
> diff --git a/support/support_record_failure.c b/support/support_record_failure.c
> index 356798f556..17ab1d80ef 100644
> --- a/support/support_record_failure.c
> +++ b/support/support_record_failure.c
> @@ -104,3 +104,11 @@ support_record_failure_reset (void)
> __atomic_store_n (&state->failed, 0, __ATOMIC_RELAXED);
> __atomic_add_fetch (&state->counter, 0, __ATOMIC_RELAXED);
> }
> +
> +int
> +support_record_failure_is_failed (void)
> +{
> + /* Relaxed MO is sufficient because we need (blocking) external
> + synchronization for reliable test error reporting anyway. */
> + return __atomic_load_n (&state->failed, __ATOMIC_RELAXED);
> +}
OK.
> diff --git a/support/tst-support_descriptors.c b/support/tst-support_descriptors.c
> new file mode 100644
> index 0000000000..34c5e1673f
> --- /dev/null
> +++ b/support/tst-support_descriptors.c
> @@ -0,0 +1,167 @@
> +/* Tests for monitoring file descriptor usage.
> + Copyright (C) 2018 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <http://www.gnu.org/licenses/>. */
> +
> +#include <fcntl.h>
> +#include <stdbool.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <support/capture_subprocess.h>
> +#include <support/check.h>
> +#include <support/descriptors.h>
> +#include <support/support.h>
> +#include <support/xunistd.h>
> +
> +/* This is the next free descriptor that the subprocess will pick. */
> +static int free_descriptor;
> +
> +static void
> +subprocess_no_change (void *closure)
> +{
> + struct support_descriptors *descrs = support_descriptors_list ();
> + int fd = xopen ("/dev/null", O_WRONLY, 0);
> + TEST_COMPARE (fd, free_descriptor);
> + xclose (fd);
> + support_descriptors_free (descrs);
> +}
> +
> +static void
> +subprocess_closed_descriptor (void *closure)
> +{
> + int fd = xopen ("/dev/null", O_WRONLY, 0);
> + TEST_COMPARE (fd, free_descriptor);
> + struct support_descriptors *descrs = support_descriptors_list ();
> + xclose (fd);
> + support_descriptors_check (descrs); /* Will report failure. */
> + puts ("EOT");
> + support_descriptors_free (descrs);
> +}
> +
> +static void
> +subprocess_opened_descriptor (void *closure)
> +{
> + struct support_descriptors *descrs = support_descriptors_list ();
> + int fd = xopen ("/dev/null", O_WRONLY, 0);
> + TEST_COMPARE (fd, free_descriptor);
> + support_descriptors_check (descrs); /* Will report failure. */
> + puts ("EOT");
> + support_descriptors_free (descrs);
> +}
> +
> +static void
> +subprocess_changed_descriptor (void *closure)
> +{
> + int fd = xopen ("/dev/null", O_WRONLY, 0);
> + TEST_COMPARE (fd, free_descriptor);
> + struct support_descriptors *descrs = support_descriptors_list ();
> + xclose (fd);
> + TEST_COMPARE (xopen ("/dev", O_DIRECTORY | O_RDONLY, 0), fd);
> + support_descriptors_check (descrs); /* Will report failure. */
> + puts ("EOT");
> + support_descriptors_free (descrs);
> +}
> +
> +static void
> +report_subprocess_output (const char *name,
> + struct support_capture_subprocess *proc)
> +{
> + printf ("info: BEGIN %s output\n"
> + "%s"
> + "info: END %s output\n",
> + name, proc->out.buffer, name);
> +}
> +
> +static int
> +do_test (void)
> +{
> + puts ("info: initial descriptor set");
> + {
> + struct support_descriptors *descrs = support_descriptors_list ();
> + support_descriptors_dump (descrs, "info: ", stdout);
> + support_descriptors_free (descrs);
> + }
> +
> + free_descriptor = xopen ("/dev/null", O_WRONLY, 0);
> + puts ("info: descriptor set with additional free descriptor");
> + {
> + struct support_descriptors *descrs = support_descriptors_list ();
> + support_descriptors_dump (descrs, "info: ", stdout);
> + support_descriptors_free (descrs);
> + }
> + TEST_VERIFY (free_descriptor >= 3);
> + xclose (free_descriptor);
> +
> + struct support_capture_subprocess proc = support_capture_subprocess
> + (&subprocess_no_change, NULL);
> + support_capture_subprocess_check (&proc, "subprocess_no_change",
> + 0, sc_allow_none);
> + support_capture_subprocess_free (&proc);
> +
> + /* Use an explicit flag to preserve failure status across
> + support_record_failure_reset calls. */
> + bool good = true;
> +
> + char *expected = xasprintf ("\nDifferences:\n"
> + "error: descriptor %d was closed\n"
> + "EOT\n",
> + free_descriptor);
> + good = good && !support_record_failure_is_failed ();
> + proc = support_capture_subprocess (&subprocess_closed_descriptor, NULL);
> + good = good && support_record_failure_is_failed ();
> + support_record_failure_reset (); /* Discard the reported error. */
> + report_subprocess_output ("subprocess_closed_descriptor", &proc);
> + TEST_VERIFY (strstr (proc.out.buffer, expected) != NULL);
> + support_capture_subprocess_check (&proc, "subprocess_closed_descriptor",
> + 0, sc_allow_stdout);
> + support_capture_subprocess_free (&proc);
> + free (expected);
> +
> + expected = xasprintf ("\nDifferences:\n"
> + "error: descriptor %d was opened (\"/dev/null\")\n"
> + "EOT\n",
> + free_descriptor);
> + good = good && !support_record_failure_is_failed ();
> + proc = support_capture_subprocess (&subprocess_opened_descriptor, NULL);
> + good = good && support_record_failure_is_failed ();
> + support_record_failure_reset (); /* Discard the reported error. */
> + report_subprocess_output ("subprocess_opened_descriptor", &proc);
> + TEST_VERIFY (strstr (proc.out.buffer, expected) != NULL);
> + support_capture_subprocess_check (&proc, "subprocess_opened_descriptor",
> + 0, sc_allow_stdout);
> + support_capture_subprocess_free (&proc);
> + free (expected);
> +
> + expected = xasprintf ("\nDifferences:\n"
> + "error: descriptor %d changed from \"/dev/null\""
> + " to \"/dev\"\n"
> + "error: descriptor %d changed ino ",
> + free_descriptor, free_descriptor);
> + good = good && !support_record_failure_is_failed ();
> + proc = support_capture_subprocess (&subprocess_changed_descriptor, NULL);
> + good = good && support_record_failure_is_failed ();
> + support_record_failure_reset (); /* Discard the reported error. */
> + report_subprocess_output ("subprocess_changed_descriptor", &proc);
> + TEST_VERIFY (strstr (proc.out.buffer, expected) != NULL);
> + support_capture_subprocess_check (&proc, "subprocess_changed_descriptor",
> + 0, sc_allow_stdout);
> + support_capture_subprocess_free (&proc);
> + free (expected);
> +
> + return !good;
> +}
> +
> +#include <support/test-driver.c>
>
OK.
--
Cheers,
Carlos.