lib/netns.c: Add comments to the code, including doxygen API docs

Change-Id: I0b20e4870bf62df0a459a621a64a4e2795340ceb
This commit is contained in:
Harald Welte 2020-04-11 11:55:53 +02:00 committed by laforge
parent 1c8ae66654
commit 20d9d154c5
1 changed files with 45 additions and 0 deletions

View File

@ -44,8 +44,13 @@
#define NETNS_PATH "/var/run/netns"
/*! default namespace of the GGSN process */
static int default_nsfd;
/*! switch to a (non-default) namespace, store existing signal mask in oldmask.
* \param[in] nsfd file descriptor representing the namespace to whch we shall switch
* \param[out] oldmask caller-provided memory location to which old signal mask is stored
* \ returns 0 on success or negative (errno) in case of error */
int switch_ns(int nsfd, sigset_t *oldmask)
{
sigset_t intmask;
@ -61,6 +66,9 @@ int switch_ns(int nsfd, sigset_t *oldmask)
return 0;
}
/*! switch back to the default namespace, restoring signal mask.
* \param[in] oldmask signal mask to restore after returning to default namespace
* \returns 0 on successs; negative errno value in case of error */
int restore_ns(sigset_t *oldmask)
{
int rc;
@ -72,25 +80,31 @@ int restore_ns(sigset_t *oldmask)
return 0;
}
/*! open a file from within specified network namespace */
int open_ns(int nsfd, const char *pathname, int flags)
{
sigset_t intmask, oldmask;
int fd;
int rc;
/* mask off all signals, store old signal mask */
if (sigfillset(&intmask) < 0)
return -errno;
if ((rc = sigprocmask(SIG_BLOCK, &intmask, &oldmask)) != 0)
return -rc;
/* associate the calling thread with namespace file descriptor */
if (setns(nsfd, CLONE_NEWNET) < 0)
return -errno;
/* open the requested file/path */
if ((fd = open(pathname, flags)) < 0)
return -errno;
/* return back to default namespace */
if (setns(default_nsfd, CLONE_NEWNET) < 0) {
close(fd);
return -errno;
}
/* restore process mask */
if ((rc = sigprocmask(SIG_SETMASK, &oldmask, NULL)) != 0) {
close(fd);
return -rc;
@ -99,26 +113,41 @@ int open_ns(int nsfd, const char *pathname, int flags)
return fd;
}
/*! create a socket in another namespace.
* Switches temporarily to namespace indicated by nsfd, creates a socket in
* that namespace and then returns to the default namespace.
* \param[in] nsfd File descriptor of the namspace in which to create socket
* \param[in] domain Domain of the socket (AF_INET, ...)
* \param[in] type Type of the socket (SOCK_STREAM, ...)
* \param[in] protocol Protocol of the socket (IPPROTO_TCP, ...)
* \returns 0 on success; negative errno in case of error */
int socket_ns(int nsfd, int domain, int type, int protocol)
{
sigset_t intmask, oldmask;
int sk;
int rc;
/* mask off all signals, store old signal mask */
if (sigfillset(&intmask) < 0)
return -errno;
if ((rc = sigprocmask(SIG_BLOCK, &intmask, &oldmask)) != 0)
return -rc;
/* associate the calling thread with namespace file descriptor */
if (setns(nsfd, CLONE_NEWNET) < 0)
return -errno;
/* create socket of requested domain/type/proto */
if ((sk = socket(domain, type, protocol)) < 0)
return -errno;
/* return back to default namespace */
if (setns(default_nsfd, CLONE_NEWNET) < 0) {
close(sk);
return -errno;
}
/* restore process mask */
if ((rc = sigprocmask(SIG_SETMASK, &oldmask, NULL)) != 0) {
close(sk);
return -rc;
@ -126,13 +155,21 @@ int socket_ns(int nsfd, int domain, int type, int protocol)
return sk;
}
/*! initialize this network namespace helper module.
* Must be called before using any other functions of this file.
* \returns 0 on success; negative errno in case of error */
int init_netns()
{
/* store the default namespace for later reference */
if ((default_nsfd = open("/proc/self/ns/net", O_RDONLY)) < 0)
return -errno;
return 0;
}
/*! create obtain file descriptor for network namespace of give name.
* Creates /var/run/netns if it doesn't exist already.
* \param[in] name Name of the network namespace (in /var/run/netns/)
* \returns File descriptor of network namespace; negative errno in case of error */
int get_nsfd(const char *name)
{
int rc;
@ -140,10 +177,12 @@ int get_nsfd(const char *name)
sigset_t intmask, oldmask;
char path[MAXPATHLEN] = NETNS_PATH;
/* create /var/run/netns, if it doesn't exist already */
rc = mkdir(path, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH);
if (rc < 0 && errno != EEXIST)
return rc;
/* create /var/run/netns/[name], if it doesn't exist already */
snprintf(path, sizeof(path), "%s/%s", NETNS_PATH, name);
fd = open(path, O_RDONLY|O_CREAT|O_EXCL, 0);
if (fd < 0) {
@ -157,24 +196,30 @@ int get_nsfd(const char *name)
if (close(fd) < 0)
return -errno;
/* mask off all signals, store old signal mask */
if (sigfillset(&intmask) < 0)
return -errno;
if ((rc = sigprocmask(SIG_BLOCK, &intmask, &oldmask)) != 0)
return -rc;
/* create a new network namespace */
if (unshare(CLONE_NEWNET) < 0)
return -errno;
if (mount("/proc/self/ns/net", path, "none", MS_BIND, NULL) < 0)
return -errno;
/* switch back to default namespace */
if (setns(default_nsfd, CLONE_NEWNET) < 0)
return -errno;
/* restore process mask */
if ((rc = sigprocmask(SIG_SETMASK, &oldmask, NULL)) != 0)
return -rc;
/* finally, open the created namespace file descriptor from default ns */
if ((fd = open(path, O_RDONLY)) < 0)
return -errno;
return fd;
}