lib/netns.c: Add comments to the code, including doxygen API docs
Change-Id: I0b20e4870bf62df0a459a621a64a4e2795340ceb
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1c8ae66654
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45
lib/netns.c
45
lib/netns.c
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@ -44,8 +44,13 @@
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#define NETNS_PATH "/var/run/netns"
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/*! default namespace of the GGSN process */
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static int default_nsfd;
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/*! switch to a (non-default) namespace, store existing signal mask in oldmask.
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* \param[in] nsfd file descriptor representing the namespace to whch we shall switch
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* \param[out] oldmask caller-provided memory location to which old signal mask is stored
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* \ returns 0 on success or negative (errno) in case of error */
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int switch_ns(int nsfd, sigset_t *oldmask)
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{
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sigset_t intmask;
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@ -61,6 +66,9 @@ int switch_ns(int nsfd, sigset_t *oldmask)
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return 0;
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}
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/*! switch back to the default namespace, restoring signal mask.
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* \param[in] oldmask signal mask to restore after returning to default namespace
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* \returns 0 on successs; negative errno value in case of error */
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int restore_ns(sigset_t *oldmask)
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{
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int rc;
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@ -72,25 +80,31 @@ int restore_ns(sigset_t *oldmask)
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return 0;
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}
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/*! open a file from within specified network namespace */
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int open_ns(int nsfd, const char *pathname, int flags)
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{
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sigset_t intmask, oldmask;
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int fd;
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int rc;
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/* mask off all signals, store old signal mask */
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if (sigfillset(&intmask) < 0)
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return -errno;
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if ((rc = sigprocmask(SIG_BLOCK, &intmask, &oldmask)) != 0)
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return -rc;
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/* associate the calling thread with namespace file descriptor */
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if (setns(nsfd, CLONE_NEWNET) < 0)
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return -errno;
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/* open the requested file/path */
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if ((fd = open(pathname, flags)) < 0)
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return -errno;
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/* return back to default namespace */
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if (setns(default_nsfd, CLONE_NEWNET) < 0) {
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close(fd);
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return -errno;
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}
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/* restore process mask */
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if ((rc = sigprocmask(SIG_SETMASK, &oldmask, NULL)) != 0) {
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close(fd);
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return -rc;
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@ -99,26 +113,41 @@ int open_ns(int nsfd, const char *pathname, int flags)
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return fd;
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}
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/*! create a socket in another namespace.
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* Switches temporarily to namespace indicated by nsfd, creates a socket in
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* that namespace and then returns to the default namespace.
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* \param[in] nsfd File descriptor of the namspace in which to create socket
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* \param[in] domain Domain of the socket (AF_INET, ...)
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* \param[in] type Type of the socket (SOCK_STREAM, ...)
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* \param[in] protocol Protocol of the socket (IPPROTO_TCP, ...)
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* \returns 0 on success; negative errno in case of error */
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int socket_ns(int nsfd, int domain, int type, int protocol)
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{
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sigset_t intmask, oldmask;
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int sk;
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int rc;
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/* mask off all signals, store old signal mask */
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if (sigfillset(&intmask) < 0)
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return -errno;
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if ((rc = sigprocmask(SIG_BLOCK, &intmask, &oldmask)) != 0)
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return -rc;
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/* associate the calling thread with namespace file descriptor */
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if (setns(nsfd, CLONE_NEWNET) < 0)
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return -errno;
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/* create socket of requested domain/type/proto */
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if ((sk = socket(domain, type, protocol)) < 0)
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return -errno;
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/* return back to default namespace */
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if (setns(default_nsfd, CLONE_NEWNET) < 0) {
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close(sk);
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return -errno;
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}
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/* restore process mask */
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if ((rc = sigprocmask(SIG_SETMASK, &oldmask, NULL)) != 0) {
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close(sk);
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return -rc;
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@ -126,13 +155,21 @@ int socket_ns(int nsfd, int domain, int type, int protocol)
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return sk;
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}
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/*! initialize this network namespace helper module.
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* Must be called before using any other functions of this file.
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* \returns 0 on success; negative errno in case of error */
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int init_netns()
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{
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/* store the default namespace for later reference */
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if ((default_nsfd = open("/proc/self/ns/net", O_RDONLY)) < 0)
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return -errno;
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return 0;
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}
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/*! create obtain file descriptor for network namespace of give name.
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* Creates /var/run/netns if it doesn't exist already.
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* \param[in] name Name of the network namespace (in /var/run/netns/)
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* \returns File descriptor of network namespace; negative errno in case of error */
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int get_nsfd(const char *name)
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{
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int rc;
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@ -140,10 +177,12 @@ int get_nsfd(const char *name)
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sigset_t intmask, oldmask;
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char path[MAXPATHLEN] = NETNS_PATH;
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/* create /var/run/netns, if it doesn't exist already */
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rc = mkdir(path, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH);
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if (rc < 0 && errno != EEXIST)
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return rc;
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/* create /var/run/netns/[name], if it doesn't exist already */
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snprintf(path, sizeof(path), "%s/%s", NETNS_PATH, name);
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fd = open(path, O_RDONLY|O_CREAT|O_EXCL, 0);
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if (fd < 0) {
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@ -157,24 +196,30 @@ int get_nsfd(const char *name)
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if (close(fd) < 0)
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return -errno;
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/* mask off all signals, store old signal mask */
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if (sigfillset(&intmask) < 0)
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return -errno;
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if ((rc = sigprocmask(SIG_BLOCK, &intmask, &oldmask)) != 0)
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return -rc;
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/* create a new network namespace */
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if (unshare(CLONE_NEWNET) < 0)
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return -errno;
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if (mount("/proc/self/ns/net", path, "none", MS_BIND, NULL) < 0)
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return -errno;
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/* switch back to default namespace */
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if (setns(default_nsfd, CLONE_NEWNET) < 0)
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return -errno;
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/* restore process mask */
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if ((rc = sigprocmask(SIG_SETMASK, &oldmask, NULL)) != 0)
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return -rc;
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/* finally, open the created namespace file descriptor from default ns */
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if ((fd = open(path, O_RDONLY)) < 0)
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return -errno;
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return fd;
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}
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