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authorDavid Herrmann <dh.herrmann@gmail.com>2015-09-22 14:09:54 +0200
committerDavid Herrmann <dh.herrmann@gmail.com>2015-09-22 14:09:54 +0200
commitd960371482d75711e61896f27ea0d3740ea69fe0 (patch)
tree6e7ffbd22d6dfb9ed71976e11999abcb93c31e9d /src/basic
parent8e112c803cb9b1ab1d564d0e5a7f06af59a2a30a (diff)
util: introduce {send,receive}_one_fd()
Introduce two new helpers that send/receive a single fd via a unix transport. Also make nspawn use them instead of hard-coding it. Based on a patch by Krzesimir Nowak.
Diffstat (limited to 'src/basic')
-rw-r--r--src/basic/util.c69
-rw-r--r--src/basic/util.h3
2 files changed, 72 insertions, 0 deletions
diff --git a/src/basic/util.c b/src/basic/util.c
index e3b2af8e02..40d9e34f85 100644
--- a/src/basic/util.c
+++ b/src/basic/util.c
@@ -6775,3 +6775,72 @@ int fgetxattr_malloc(int fd, const char *name, char **value) {
return -errno;
}
}
+
+int send_one_fd(int transport_fd, int fd) {
+ union {
+ struct cmsghdr cmsghdr;
+ uint8_t buf[CMSG_SPACE(sizeof(int))];
+ } control = {};
+ struct msghdr mh = {
+ .msg_control = &control,
+ .msg_controllen = sizeof(control),
+ };
+ struct cmsghdr *cmsg;
+ ssize_t k;
+
+ assert(transport_fd >= 0);
+ assert(fd >= 0);
+
+ cmsg = CMSG_FIRSTHDR(&mh);
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+ cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+ memcpy(CMSG_DATA(cmsg), &fd, sizeof(int));
+
+ mh.msg_controllen = CMSG_SPACE(sizeof(int));
+ k = sendmsg(transport_fd, &mh, MSG_NOSIGNAL);
+ if (k < 0)
+ return -errno;
+
+ return 0;
+}
+
+int receive_one_fd(int transport_fd) {
+ union {
+ struct cmsghdr cmsghdr;
+ uint8_t buf[CMSG_SPACE(sizeof(int))];
+ } control = {};
+ struct msghdr mh = {
+ .msg_control = &control,
+ .msg_controllen = sizeof(control),
+ };
+ struct cmsghdr *cmsg;
+ ssize_t k;
+
+ assert(transport_fd >= 0);
+
+ /*
+ * Receive a single FD via @transport_fd. We don't care for the
+ * transport-type, but the caller must assure that no other CMSG types
+ * than SCM_RIGHTS is enabled. We also retrieve a single FD at most, so
+ * for packet-based transports, the caller must ensure to send only a
+ * single FD per packet.
+ * This is best used in combination with send_one_fd().
+ */
+
+ k = recvmsg(transport_fd, &mh, MSG_NOSIGNAL | MSG_CMSG_CLOEXEC);
+ if (k < 0)
+ return -errno;
+
+ cmsg = CMSG_FIRSTHDR(&mh);
+ if (!cmsg || CMSG_NXTHDR(&mh, cmsg) ||
+ cmsg->cmsg_level != SOL_SOCKET ||
+ cmsg->cmsg_type != SCM_RIGHTS ||
+ cmsg->cmsg_len != CMSG_LEN(sizeof(int)) ||
+ *(const int *)CMSG_DATA(cmsg) < 0) {
+ cmsg_close_all(&mh);
+ return -EIO;
+ }
+
+ return *(const int *)CMSG_DATA(cmsg);
+}
diff --git a/src/basic/util.h b/src/basic/util.h
index 8abaa740b2..905f375263 100644
--- a/src/basic/util.h
+++ b/src/basic/util.h
@@ -938,3 +938,6 @@ int reset_uid_gid(void);
int getxattr_malloc(const char *path, const char *name, char **value, bool allow_symlink);
int fgetxattr_malloc(int fd, const char *name, char **value);
+
+int send_one_fd(int transport_fd, int fd);
+int receive_one_fd(int transport_fd);