diff options
author | Harald Welte <laforge@osmocom.org> | 2020-04-11 11:55:53 +0200 |
---|---|---|
committer | laforge <laforge@osmocom.org> | 2020-04-14 13:19:04 +0000 |
commit | 20d9d154c506f1d7dd7bf8fa0581bbf22be4630f (patch) | |
tree | 4f4f068258312be06c556733a84616e308f60c21 /lib | |
parent | 1c8ae666548d350701c3645a97792776203ff200 (diff) |
lib/netns.c: Add comments to the code, including doxygen API docs
Change-Id: I0b20e4870bf62df0a459a621a64a4e2795340ceb
Diffstat (limited to 'lib')
-rw-r--r-- | lib/netns.c | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/lib/netns.c b/lib/netns.c index 58ae036..1e77a04 100644 --- a/lib/netns.c +++ b/lib/netns.c @@ -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; } |