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Draft: nsenter Avoid unnecessary looping by keeping reference to each namespace #2387

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Draft: nsenter Avoid unnecessary looping by keeping reference to each namespace #2387

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48 changes: 22 additions & 26 deletions sys-utils/nsenter.c
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,15 @@ static struct namespace_file {
{ .nstype = 0, .name = NULL, .fd = -1 }
};

static struct namespace_file* user_namespace_file = &namespace_files[0];
static struct namespace_file* cgroup_namespace_file = &namespace_files[1];
static struct namespace_file* ipc_namespace_file = &namespace_files[2];
static struct namespace_file* uts_namespace_file = &namespace_files[3];
static struct namespace_file* net_namespace_file = &namespace_files[4];
static struct namespace_file* pid_namespace_file = &namespace_files[5];
static struct namespace_file* mnt_namespace_file = &namespace_files[6];
static struct namespace_file* time_namespace_file = &namespace_files[7];

static void __attribute__((__noreturn__)) usage(void)
{
FILE *out = stdout;
Expand Down Expand Up @@ -136,13 +145,9 @@ static int cgroup_procs_fd = -1;
static void set_parent_user_ns_fd(void)
{
struct namespace_file *nsfile = NULL;
struct namespace_file *user_nsfile = NULL;
int parent_ns = -1;

for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
if (nsfile->nstype == CLONE_NEWUSER)
user_nsfile = nsfile;

if (nsfile->fd == -1)
continue;

Expand All @@ -155,8 +160,8 @@ static void set_parent_user_ns_fd(void)

if (parent_ns < 0)
errx(EXIT_FAILURE, _("no namespaces to get parent of"));
if (user_nsfile)
user_nsfile->fd = parent_ns;

user_namespace_file->fd = parent_ns;
}


Expand All @@ -182,18 +187,9 @@ static void open_target_fd(int *fd, const char *type, const char *path)
err(EXIT_FAILURE, _("cannot open %s"), path);
}

static void open_namespace_fd(int nstype, const char *path)
static void open_namespace_fd(struct namespace_file* nsfile, const char *path)
{
struct namespace_file *nsfile;

for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
if (nstype != nsfile->nstype)
continue;

open_target_fd(&nsfile->fd, nsfile->name, path);
return;
}
/* This should never happen */
open_target_fd(&nsfile->fd, nsfile->name, path);
assert(nsfile->nstype);
}

Expand Down Expand Up @@ -399,49 +395,49 @@ int main(int argc, char *argv[])
break;
case 'm':
if (optarg)
open_namespace_fd(CLONE_NEWNS, optarg);
open_namespace_fd(mnt_namespace_file, optarg);
else
namespaces |= CLONE_NEWNS;
break;
case 'u':
if (optarg)
open_namespace_fd(CLONE_NEWUTS, optarg);
open_namespace_fd(uts_namespace_file, optarg);
else
namespaces |= CLONE_NEWUTS;
break;
case 'i':
if (optarg)
open_namespace_fd(CLONE_NEWIPC, optarg);
open_namespace_fd(ipc_namespace_file, optarg);
else
namespaces |= CLONE_NEWIPC;
break;
case 'n':
if (optarg)
open_namespace_fd(CLONE_NEWNET, optarg);
open_namespace_fd(net_namespace_file, optarg);
else
namespaces |= CLONE_NEWNET;
break;
case 'p':
if (optarg)
open_namespace_fd(CLONE_NEWPID, optarg);
open_namespace_fd(pid_namespace_file, optarg);
else
namespaces |= CLONE_NEWPID;
break;
case 'C':
if (optarg)
open_namespace_fd(CLONE_NEWCGROUP, optarg);
open_namespace_fd(cgroup_namespace_file, optarg);
else
namespaces |= CLONE_NEWCGROUP;
break;
case 'U':
if (optarg)
open_namespace_fd(CLONE_NEWUSER, optarg);
open_namespace_fd(user_namespace_file, optarg);
else
namespaces |= CLONE_NEWUSER;
break;
case 'T':
if (optarg)
open_namespace_fd(CLONE_NEWTIME, optarg);
open_namespace_fd(time_namespace_file, optarg);
else
namespaces |= CLONE_NEWTIME;
break;
Expand Down Expand Up @@ -540,7 +536,7 @@ int main(int argc, char *argv[])
*/
for (nsfile = namespace_files; nsfile->nstype; nsfile++)
if (nsfile->nstype & namespaces)
open_namespace_fd(nsfile->nstype, NULL);
open_namespace_fd(nsfile, NULL);
if (do_rd)
open_target_fd(&root_fd, "root", NULL);
if (do_wd)
Expand Down