From: Michal Privoznik <mprivozn(a)redhat.com&gt; Currently, when somebody wants to debug the NSS plugin, they have to change a line in libvirt_nss.h (to enable debug printings) and recompile the module. This may work for us, developers, but we can not expect this from users. For now, this turns debug printings unconditionally on. Making it conditional on an envvar is handled in the next commit. Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- build-aux/syntax-check.mk | 2 +- tools/nss/libvirt_nss.h | 30 +-------------- tools/nss/libvirt_nss_log.c | 76 +++++++++++++++++++++++++++++++++++++ tools/nss/libvirt_nss_log.h | 38 +++++++++++++++++++ tools/nss/meson.build | 1 + 5 files changed, 117 insertions(+), 30 deletions(-) create mode 100644 tools/nss/libvirt_nss_log.c create mode 100644 tools/nss/libvirt_nss_log.h diff --git a/build-aux/syntax-check.mk b/build-aux/syntax-check.mk index 1303a0ce7e..541b2c5016 100644 --- a/build-aux/syntax-check.mk +++ b/build-aux/syntax-check.mk @@ -1421,7 +1421,7 @@ exclude_file_name_regexp--sc_prohibit_canonicalize_file_name = \ ^(build-aux/syntax-check\.mk|tests/virfilemock\.c)$$ exclude_file_name_regexp--sc_prohibit_raw_allocation = \ - ^(docs/advanced-tests\.rst|src/util/viralloc\.[ch]|examples/.*|tests/(securityselinuxhelper|(vircgroup|nss)mock|commandhelper)\.c|tools/wireshark/src/packet-libvirt\.c|tools/nss/libvirt_nss(_leases|_macs)?\.[ch])$$ + ^(docs/advanced-tests\.rst|src/util/viralloc\.[ch]|examples/.*|tests/(securityselinuxhelper|(vircgroup|nss)mock|commandhelper)\.c|tools/wireshark/src/packet-libvirt\.c|tools/nss/libvirt_nss(_leases|_log|_macs)?\.[ch])$$ exclude_file_name_regexp--sc_prohibit_readlink = \ ^src/(util/virutil|lxc/lxc_container)\.c$$ diff --git a/tools/nss/libvirt_nss.h b/tools/nss/libvirt_nss.h index 84db044409..e09fce9715 100644 --- a/tools/nss/libvirt_nss.h +++ b/tools/nss/libvirt_nss.h @@ -31,35 +31,7 @@ #include <netdb.h> #include <stdlib.h> - -#if 0 -# include <errno.h> -# include <stdio.h> -# include <string.h> -# define NULLSTR(s) ((s) ? (s) : "<null>") -# define ERROR(...) \ -do { \ - int saved_errno = errno; \ - const size_t ebuf_size = 512; \ - g_autofree char *ebuf = calloc(ebuf_size, sizeof(*ebuf)); \ - if (ebuf) \ - strerror_r(saved_errno, ebuf, ebuf_size); \ - fprintf(stderr, "ERROR %s:%d : ", __FUNCTION__, __LINE__); \ - fprintf(stderr, __VA_ARGS__); \ - fprintf(stderr, " : %s\n", NULLSTR(ebuf)); \ - fprintf(stderr, "\n"); \ -} while (0) - -# define DEBUG(...) \ -do { \ - fprintf(stderr, "DEBUG %s:%d : ", __FUNCTION__, __LINE__); \ - fprintf(stderr, __VA_ARGS__); \ - fprintf(stderr, "\n"); \ -} while (0) -#else -# define ERROR(...) do { } while (0) -# define DEBUG(...) do { } while (0) -#endif +#include "libvirt_nss_log.h" #if !defined(LIBVIRT_NSS_GUEST) # define NSS_NAME(s) _nss_libvirt_##s##_r diff --git a/tools/nss/libvirt_nss_log.c b/tools/nss/libvirt_nss_log.c new file mode 100644 index 0000000000..0863897c07 --- /dev/null +++ b/tools/nss/libvirt_nss_log.c @@ -0,0 +1,76 @@ +/* + * libvirt_nss_log: Logging for Name Service Switch plugin + * + * Copyright (C) 2025 Red Hat, Inc. + * + * This 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. + * + * This 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 this library. If not, see + * <http://www.gnu.org/licenses/>;. + */ + +#include <config.h> + +#include <errno.h> +#include <stdio.h> +#include <string.h> +#include <stdarg.h> + +#include "libvirt_nss_log.h" +#include "libvirt_nss.h" + +#define NULLSTR(s) ((s) ? (s) : "<null>") + +static const char * __attribute__((returns_nonnull)) +nssLogPriorityToString(nssLogPriority prio) +{ + switch (prio) { + case NSS_DEBUG: + return "DEBUG"; + case NSS_ERROR: + return "ERROR"; + } + + return ""; +} + +void +nssLog(nssLogPriority prio, + const char *func, + int linenr, + const char *fmt, ...) +{ + int saved_errno = errno; + const size_t ebuf_size = 512; + g_autofree char *ebuf = NULL; + va_list ap; + + fprintf(stderr, "%s %s:%d : ", nssLogPriorityToString(prio), func, linenr); + + va_start(ap, fmt); + vfprintf(stderr, fmt, ap); + va_end(ap); + + switch (prio) { + case NSS_DEBUG: + break; + + case NSS_ERROR: + ebuf = calloc(ebuf_size, sizeof(*ebuf)); + if (ebuf) + strerror_r(saved_errno, ebuf, ebuf_size); + fprintf(stderr, " : %s", NULLSTR(ebuf)); + break; + } + + fprintf(stderr, "\n"); +} diff --git a/tools/nss/libvirt_nss_log.h b/tools/nss/libvirt_nss_log.h new file mode 100644 index 0000000000..bac64d4bc7 --- /dev/null +++ b/tools/nss/libvirt_nss_log.h @@ -0,0 +1,38 @@ +/* + * libvirt_nss_log: Logging for Name Service Switch plugin + * + * Copyright (C) 2025 Red Hat, Inc. + * + * This 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. + * + * This 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 this library. If not, see + * <http://www.gnu.org/licenses/>;. + */ + +#pragma once + +typedef enum { + NSS_DEBUG, + NSS_ERROR, +} nssLogPriority; + +#define DEBUG(...) \ + nssLog(NSS_DEBUG, __FUNCTION__, __LINE__, __VA_ARGS__) + +#define ERROR(...) \ + nssLog(NSS_ERROR, __FUNCTION__, __LINE__, __VA_ARGS__) + +void +nssLog(nssLogPriority prio, + const char *func, + int linenr, + const char *fmt, ...) __attribute__ ((format(printf, 4, 5))); diff --git a/tools/nss/meson.build b/tools/nss/meson.build index 38bba2d616..5893952adc 100644 --- a/tools/nss/meson.build +++ b/tools/nss/meson.build @@ -13,6 +13,7 @@ endif nss_sources = [ 'libvirt_nss.c', 'libvirt_nss_leases.c', + 'libvirt_nss_log.c', ] nss_guest_sources = [ -- 2.49.0

From: Michal Privoznik <mprivozn(a)redhat.com&gt; As promised in previous commit, make NSS modules silent by default and enable debug printings if LIBVIRT_NSS_DEBUG envvar is set. Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- docs/nss.rst | 13 +++++++++++++ tools/nss/libvirt_nss_log.c | 4 ++++ tools/nss/libvirt_nss_log.h | 2 ++ 3 files changed, 19 insertions(+) diff --git a/docs/nss.rst b/docs/nss.rst index be137d987b..3df85cee0a 100644 --- a/docs/nss.rst +++ b/docs/nss.rst @@ -111,6 +111,19 @@ their IP addresses in any other way (usermode networking, assigned network devices and so on) will not be able to have their hostnames resolved through it. +Debugging +--------- + +:since:`Since 11.5.0` both NSS modules check for ``LIBVIRT_NSS_DEBUG`` +environment variable¸ which if set to any value turns on printing of debug and +error messages onto standard error output. This can be useful when debugging +either of the module. + +:: + + $ LIBVIRT_NSS_DEBUG=1 getent hosts mydomain + + Alternatives ------------ diff --git a/tools/nss/libvirt_nss_log.c b/tools/nss/libvirt_nss_log.c index 0863897c07..9a28a91800 100644 --- a/tools/nss/libvirt_nss_log.c +++ b/tools/nss/libvirt_nss_log.c @@ -24,6 +24,7 @@ #include <stdio.h> #include <string.h> #include <stdarg.h> +#include <stdlib.h> #include "libvirt_nss_log.h" #include "libvirt_nss.h" @@ -54,6 +55,9 @@ nssLog(nssLogPriority prio, g_autofree char *ebuf = NULL; va_list ap; + if (!getenv(NSS_LOG_ENV_VAR)) + return; + fprintf(stderr, "%s %s:%d : ", nssLogPriorityToString(prio), func, linenr); va_start(ap, fmt); diff --git a/tools/nss/libvirt_nss_log.h b/tools/nss/libvirt_nss_log.h index bac64d4bc7..25926fb6de 100644 --- a/tools/nss/libvirt_nss_log.h +++ b/tools/nss/libvirt_nss_log.h @@ -31,6 +31,8 @@ typedef enum { #define ERROR(...) \ nssLog(NSS_ERROR, __FUNCTION__, __LINE__, __VA_ARGS__) +#define NSS_LOG_ENV_VAR "LIBVIRT_NSS_DEBUG" + void nssLog(nssLogPriority prio, const char *func, -- 2.49.0

From: Michal Privoznik <mprivozn(a)redhat.com&gt; Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- tools/nss/libvirt_nss_log.c | 7 ++++++- tools/nss/libvirt_nss_log.h | 7 ++++--- 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/tools/nss/libvirt_nss_log.c b/tools/nss/libvirt_nss_log.c index 9a28a91800..04fc049376 100644 --- a/tools/nss/libvirt_nss_log.c +++ b/tools/nss/libvirt_nss_log.c @@ -46,6 +46,7 @@ nssLogPriorityToString(nssLogPriority prio) void nssLog(nssLogPriority prio, + const char *filename, const char *func, int linenr, const char *fmt, ...) @@ -58,7 +59,11 @@ nssLog(nssLogPriority prio, if (!getenv(NSS_LOG_ENV_VAR)) return; - fprintf(stderr, "%s %s:%d : ", nssLogPriorityToString(prio), func, linenr); + if ((filename = strrchr(filename, '/'))) + filename++; + + fprintf(stderr, "%s %s:%s():%d : ", + nssLogPriorityToString(prio), NULLSTR(filename), func, linenr); va_start(ap, fmt); vfprintf(stderr, fmt, ap); diff --git a/tools/nss/libvirt_nss_log.h b/tools/nss/libvirt_nss_log.h index 25926fb6de..60696c7b08 100644 --- a/tools/nss/libvirt_nss_log.h +++ b/tools/nss/libvirt_nss_log.h @@ -26,15 +26,16 @@ typedef enum { } nssLogPriority; #define DEBUG(...) \ - nssLog(NSS_DEBUG, __FUNCTION__, __LINE__, __VA_ARGS__) + nssLog(NSS_DEBUG, __FILE__, __FUNCTION__, __LINE__, __VA_ARGS__) #define ERROR(...) \ - nssLog(NSS_ERROR, __FUNCTION__, __LINE__, __VA_ARGS__) + nssLog(NSS_ERROR, __FILE__, __FUNCTION__, __LINE__, __VA_ARGS__) #define NSS_LOG_ENV_VAR "LIBVIRT_NSS_DEBUG" void nssLog(nssLogPriority prio, + const char *filename, const char *func, int linenr, - const char *fmt, ...) __attribute__ ((format(printf, 4, 5))); + const char *fmt, ...) __attribute__ ((format(printf, 5, 6))); -- 2.49.0

From: Michal Privoznik <mprivozn(a)redhat.com&gt; It may help in case the NSS plugin ever faces a corrupted JSON Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- tools/nss/libvirt_nss_leases.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/tools/nss/libvirt_nss_leases.c b/tools/nss/libvirt_nss_leases.c index 6624df2928..c1b4cd7392 100644 --- a/tools/nss/libvirt_nss_leases.c +++ b/tools/nss/libvirt_nss_leases.c @@ -265,10 +265,9 @@ findLeases(const char *file, json_tokener *tok = NULL; enum json_tokener_error jerr = json_tokener_error_parse_eof; int jsonflags = JSON_TOKENER_STRICT | JSON_TOKENER_VALIDATE_UTF8; - char line[1024]; size_t nreadTotal = 0; - int rv; + DEBUG("Processing %s", file); if ((fd = open(file, O_RDONLY)) < 0) { ERROR("Cannot open %s", file); goto cleanup; @@ -282,7 +281,11 @@ findLeases(const char *file, json_tokener_set_flags(tok, jsonflags); do { - rv = read(fd, line, sizeof(line)); + char line[1024] = { 0 }; + ssize_t rv; + + rv = read(fd, line, sizeof(line) - 1); + DEBUG("read: rv=%zd line='%s'", rv, line); if (rv < 0) goto cleanup; if (rv == 0) @@ -293,6 +296,9 @@ findLeases(const char *file, jerr = json_tokener_get_error(tok); } while (jerr == json_tokener_continue); + DEBUG("Done reading, nreadTotal=%zu, jerr=%d '%s'", + nreadTotal, (int)jerr, json_tokener_error_desc(jerr)); + if (nreadTotal == 0) { ret = 0; goto cleanup; -- 2.49.0