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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* namespace.c
*/
#include <sys/statvfs.h>
#include <fcntl.h>
#include <dirent.h>
#include <limits.h>
#include <linux/net_namespace.h>
#include "utils.h"
#include "namespace.h"
#include "libnetlink.h"
static void bind_etc(const char *name)
{
char etc_netns_path[sizeof(NETNS_ETC_DIR) + NAME_MAX];
char netns_name[PATH_MAX];
char etc_name[PATH_MAX];
struct dirent *entry;
DIR *dir;
if (strlen(name) >= NAME_MAX)
return;
snprintf(etc_netns_path, sizeof(etc_netns_path), "%s/%s", NETNS_ETC_DIR, name);
dir = opendir(etc_netns_path);
if (!dir)
return;
while ((entry = readdir(dir)) != NULL) {
if (strcmp(entry->d_name, ".") == 0)
continue;
if (strcmp(entry->d_name, "..") == 0)
continue;
snprintf(netns_name, sizeof(netns_name), "%s/%s", etc_netns_path, entry->d_name);
snprintf(etc_name, sizeof(etc_name), "/etc/%s", entry->d_name);
if (mount(netns_name, etc_name, "none", MS_BIND, NULL) < 0) {
fprintf(stderr, "Bind %s -> %s failed: %s\n",
netns_name, etc_name, strerror(errno));
}
}
closedir(dir);
}
int netns_switch(char *name)
{
char net_path[PATH_MAX];
int netns;
unsigned long mountflags = 0;
struct statvfs fsstat;
snprintf(net_path, sizeof(net_path), "%s/%s", NETNS_RUN_DIR, name);
netns = open(net_path, O_RDONLY | O_CLOEXEC);
if (netns < 0) {
fprintf(stderr, "Cannot open network namespace \"%s\": %s\n",
name, strerror(errno));
return -1;
}
if (setns(netns, CLONE_NEWNET) < 0) {
fprintf(stderr, "setting the network namespace \"%s\" failed: %s\n",
name, strerror(errno));
close(netns);
return -1;
}
close(netns);
if (unshare(CLONE_NEWNS) < 0) {
fprintf(stderr, "unshare failed: %s\n", strerror(errno));
return -1;
}
/* Don't let any mounts propagate back to the parent */
if (mount("", "/", "none", MS_SLAVE | MS_REC, NULL)) {
fprintf(stderr, "\"mount --make-rslave /\" failed: %s\n",
strerror(errno));
return -1;
}
/* Mount a version of /sys that describes the network namespace */
if (umount2("/sys", MNT_DETACH) < 0) {
/* If this fails, perhaps there wasn't a sysfs instance mounted. Good. */
if (statvfs("/sys", &fsstat) == 0) {
/* We couldn't umount the sysfs, we'll attempt to overlay it.
* A read-only instance can't be shadowed with a read-write one. */
if (fsstat.f_flag & ST_RDONLY)
mountflags = MS_RDONLY;
}
}
if (mount(name, "/sys", "sysfs", mountflags, NULL) < 0) {
fprintf(stderr, "mount of /sys failed: %s\n",strerror(errno));
return -1;
}
/* Setup bind mounts for config files in /etc */
bind_etc(name);
return 0;
}
int netns_get_fd(const char *name)
{
char pathbuf[PATH_MAX];
const char *path, *ptr;
path = name;
ptr = strchr(name, '/');
if (!ptr) {
snprintf(pathbuf, sizeof(pathbuf), "%s/%s",
NETNS_RUN_DIR, name );
path = pathbuf;
}
return open(path, O_RDONLY);
}
int netns_foreach(int (*func)(char *nsname, void *arg), void *arg)
{
DIR *dir;
struct dirent *entry;
dir = opendir(NETNS_RUN_DIR);
if (!dir) {
if (errno == ENOENT)
return 0;
fprintf(stderr, "Failed to open directory %s: %s\n",
NETNS_RUN_DIR, strerror(errno));
return -1;
}
while ((entry = readdir(dir)) != NULL) {
if (strcmp(entry->d_name, ".") == 0)
continue;
if (strcmp(entry->d_name, "..") == 0)
continue;
if (func(entry->d_name, arg))
break;
}
closedir(dir);
return 0;
}
int netns_id_from_name(struct rtnl_handle *rtnl, const char *name)
{
struct {
struct nlmsghdr n;
struct rtgenmsg g;
char buf[1024];
} req = {
.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtgenmsg)),
.n.nlmsg_flags = NLM_F_REQUEST,
.n.nlmsg_type = RTM_GETNSID,
.g.rtgen_family = AF_UNSPEC,
};
struct nlmsghdr *answer;
struct rtattr *tb[NETNSA_MAX + 1];
struct rtgenmsg *rthdr;
int len, fd, ret = -1;
fd = netns_get_fd(name);
if (fd < 0)
return fd;
addattr32(&req.n, 1024, NETNSA_FD, fd);
if (rtnl_talk(rtnl, &req.n, &answer) < 0) {
close(fd);
return -2;
}
close(fd);
/* Validate message and parse attributes */
if (answer->nlmsg_type == NLMSG_ERROR)
goto out;
rthdr = NLMSG_DATA(answer);
len = answer->nlmsg_len - NLMSG_SPACE(sizeof(*rthdr));
if (len < 0)
goto out;
parse_rtattr(tb, NETNSA_MAX, NETNS_RTA(rthdr), len);
if (tb[NETNSA_NSID])
ret = rta_getattr_s32(tb[NETNSA_NSID]);
out:
free(answer);
return ret;
}
struct netns_name_from_id_ctx {
int32_t id;
char *name;
struct rtnl_handle *rth;
};
static int netns_name_from_id_func(char *nsname, void *arg)
{
struct netns_name_from_id_ctx *ctx = arg;
int32_t ret;
ret = netns_id_from_name(ctx->rth, nsname);
if (ret < 0 || ret != ctx->id)
return 0;
ctx->name = strdup(nsname);
return 1;
}
char *netns_name_from_id(int32_t id)
{
struct rtnl_handle rth;
struct netns_name_from_id_ctx ctx = {
.id = id,
.rth = &rth,
};
if (rtnl_open(&rth, 0) < 0)
return NULL;
netns_foreach(netns_name_from_id_func, &ctx);
rtnl_close(&rth);
return ctx.name;
}
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