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// SPDX-License-Identifier: GPL-2.0
/* ulogd namespace helper
*
* (C) 2025 The netfilter project
*
* Helper library to switch linux namespaces, primarily network. Provides
* ulogd-internally a stable api regardless whether namespace support is
* compiled in. Library-internally uses conditional compilation to allow the
* wanted level (full/none) of namespace support. Namespaces can be specified
* as open file descriptor or file path.
*/
#include "config.h"
/* Enable GNU extension */
#define _GNU_SOURCE 1
#include <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <string.h>
#include <unistd.h>
#include "ulogd/ulogd.h"
#include "ulogd/namespace.h"
#ifdef ENABLE_NAMESPACE
/**
* open_namespace_path() - Open a namespace link by path.
* @ns_path: Path of the file to open.
*
* Effectively just a wrapper around the open() syscall with fixed flags
* suitable for namespaces.
*
* Return: Open fd on success, -1 on error (and set errno).
*/
static int open_namespace_path(const char *const ns_path) {
return open(ns_path, O_RDONLY | O_CLOEXEC);
}
/**
* SELF_NAMESPACE_PATH() - Path for own current namespace.
* @x: Name of the namespace link.
*
* Return: String-constant of the absolute path to the namespace link.
*/
#define SELF_NAMESPACE_PATH(x) "/proc/self/ns/" #x
/**
* open_source_namespace() - Get file descriptor to current namespace.
* @nstype: Namespace type, use one of the CLONE_NEW* constants.
*
* Return: Open fd on success, -1 on error.
*/
static int open_source_namespace(const int nstype) {
const char *ns_path = NULL;
int ns_fd = -1;
switch (nstype) {
case CLONE_NEWNET:
ns_path = SELF_NAMESPACE_PATH(net);
break;
default:
ulogd_log(ULOGD_FATAL,
"unsupported namespace type: %d\n", nstype);
return -1;
}
ns_fd = open_namespace_path(ns_path);
if (ns_fd < 0) {
ulogd_log(ULOGD_FATAL,
"error opening namespace '%s': %s\n",
ns_path, strerror(errno));
return -1;
}
return ns_fd;
}
#else
/* These constants are used by the nstype-specific functions, and need to be
* defined even when no namespace support is available because only the generic
* functions will error.
*/
#ifndef CLONE_NEWNET
#define CLONE_NEWNET -1
#endif
#endif /* ENABLE_NAMESPACE */
/**
* join_namespace_fd() - Join a namespace by file descriptor.
* @nstype: Namespace type, use one of the CLONE_NEW* constants.
* @target_ns_fd: Open file descriptor of the namespace to join. Will be closed
* after successful join.
* @source_ns_fd_ptr: If not NULL, writes an open fd of the previous namespace
* to it if join was successful. May point to negative value
* after return.
*
* Return: ULOGD_IRET_OK on success, ULOGD_IRET_ERR otherwise.
*/
static int join_namespace_fd(const int nstype, const int target_ns_fd,
int *const source_ns_fd_ptr)
{
#ifdef ENABLE_NAMESPACE
if (target_ns_fd < 0) {
ulogd_log(ULOGD_DEBUG, "invalid target namespace fd\n");
return ULOGD_IRET_ERR;
}
if (source_ns_fd_ptr != NULL) {
*source_ns_fd_ptr = open_source_namespace(nstype);
if (*source_ns_fd_ptr < 0) {
ulogd_log(ULOGD_FATAL,
"error opening source namespace\n");
return ULOGD_IRET_ERR;
}
}
if (setns(target_ns_fd, nstype) < 0) {
ulogd_log(ULOGD_FATAL, "error joining target namespace: %s\n",
strerror(errno));
if (source_ns_fd_ptr != NULL) {
if (close(*source_ns_fd_ptr) < 0) {
ulogd_log(ULOGD_NOTICE,
"error closing source namespace: %s\n",
strerror(errno));
}
*source_ns_fd_ptr = -1;
}
return ULOGD_IRET_ERR;
}
ulogd_log(ULOGD_DEBUG, "successfully switched namespace\n");
if (close(target_ns_fd) < 0) {
ulogd_log(ULOGD_NOTICE, "error closing target namespace: %s\n",
strerror(errno));
}
return ULOGD_IRET_OK;
#else
if (source_ns_fd_ptr != NULL) {
*source_ns_fd_ptr = -1;
}
ulogd_log(ULOGD_FATAL,
"ulogd was compiled without linux namespace support.\n");
return ULOGD_IRET_ERR;
#endif /* ENABLE_NAMESPACE */
}
/**
* join_namespace_path() - Join a namespace by path.
* @nstype: Namespace type, use one of the CLONE_NEW* constants.
* @target_ns_path: Path of the namespace to join.
* @source_ns_fd_ptr: If not NULL, writes an open fd of the previous namespace
* to it if join was successful. May point to negative value
* after return.
*
* Return: ULOGD_IRET_OK on success, ULOGD_IRET_ERR otherwise.
*/
static int join_namespace_path(const int nstype, const char *const target_ns_path,
int *const source_ns_fd_ptr)
{
#ifdef ENABLE_NAMESPACE
int target_ns_fd, ret;
target_ns_fd = open_namespace_path(target_ns_path);
if (target_ns_fd < 0) {
ulogd_log(ULOGD_FATAL, "error opening target namespace: %s\n",
strerror(errno));
return ULOGD_IRET_ERR;
}
ret = join_namespace_fd(nstype, target_ns_fd, source_ns_fd_ptr);
if (ret != ULOGD_IRET_OK) {
if (close(target_ns_fd) < 0) {
ulogd_log(ULOGD_NOTICE,
"error closing target namespace: %s\n",
strerror(errno));
}
return ULOGD_IRET_ERR;
}
return ULOGD_IRET_OK;
#else
return join_namespace_fd(nstype, -1, source_ns_fd_ptr);
#endif /* ENABLE_NAMESPACE */
}
/**
* join_netns_fd() - Join a network namespace by file descriptor.
* @target_netns_fd: Open file descriptor of the network namespace to join. Will
* be closed after successful join.
* @source_netns_fd_ptr: If not NULL, writes an open fd of the previous network
* namespace to it if join was successful. May point to
* negative value after return.
*
* Return: ULOGD_IRET_OK on success, ULOGD_IRET_ERR otherwise.
*/
int join_netns_fd(const int target_netns_fd, int *const source_netns_fd_ptr)
{
return join_namespace_fd(CLONE_NEWNET, target_netns_fd,
source_netns_fd_ptr);
}
/**
* join_netns_path() - Join a network namespace by path.
* @target_netns_path: Path of the network namespace to join.
* @source_netns_fd_ptr: If not NULL, writes an open fd of the previous network
* namespace to it if join was successful. May point to
* negative value after return.
*
* Return: ULOGD_IRET_OK on success, ULOGD_IRET_ERR otherwise.
*/
int join_netns_path(const char *const target_netns_path,
int *const source_netns_fd_ptr)
{
return join_namespace_path(CLONE_NEWNET, target_netns_path,
source_netns_fd_ptr);
}
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