[ovs-dev] [worker 03/12] socket-util: Add functions for sending fds over Unix domain sockets.
Ben Pfaff
blp at nicira.com
Wed May 23 00:19:06 UTC 2012
These will be used in upcoming commits.
This commit also adds corresponding definitions to the "sparse" header,
so that sparse still works.
Signed-off-by: Ben Pfaff <blp at nicira.com>
---
include/sparse/sys/socket.h | 31 +++++
lib/socket-util.c | 255 +++++++++++++++++++++++++++++++++++++++++++
lib/socket-util.h | 24 ++++
3 files changed, 310 insertions(+), 0 deletions(-)
diff --git a/include/sparse/sys/socket.h b/include/sparse/sys/socket.h
index d7e17ea..13f61e5 100644
--- a/include/sparse/sys/socket.h
+++ b/include/sparse/sys/socket.h
@@ -47,6 +47,37 @@ struct msghdr {
int msg_flags;
};
+struct cmsghdr {
+ size_t cmsg_len;
+ int cmsg_level;
+ int cmsg_type;
+ unsigned char cmsg_data[];
+};
+
+#define __CMSG_ALIGNTO sizeof(size_t)
+#define CMSG_ALIGN(LEN) \
+ (((LEN) + __CMSG_ALIGNTO - 1) / __CMSG_ALIGNTO * __CMSG_ALIGNTO)
+#define CMSG_DATA(CMSG) ((CMSG)->cmsg_data)
+#define CMSG_LEN(LEN) (sizeof(struct cmsghdr) + (LEN))
+#define CMSG_SPACE(LEN) CMSG_ALIGN(CMSG_LEN(LEN))
+#define CMSG_FIRSTHDR(MSG) \
+ ((MSG)->msg_controllen ? (struct cmsghdr *) (MSG)->msg_control : NULL)
+#define CMSG_NXTHDR(MSG, CMSG) __cmsg_nxthdr(MSG, CMSG)
+
+static inline struct cmsghdr *
+__cmsg_nxthdr(struct msghdr *msg, struct cmsghdr *cmsg)
+{
+ size_t ofs = (char *) cmsg - (char *) msg->msg_control;
+ size_t next_ofs = ofs + CMSG_ALIGN(cmsg->cmsg_len);
+ return (next_ofs < msg->msg_controllen
+ ? (void *) ((char *) msg->msg_control + next_ofs)
+ : NULL);
+}
+
+enum {
+ SCM_RIGHTS = 1
+};
+
enum {
SOCK_DGRAM,
SOCK_RAW,
diff --git a/lib/socket-util.c b/lib/socket-util.c
index 939cd90..d58e12d 100644
--- a/lib/socket-util.c
+++ b/lib/socket-util.c
@@ -35,6 +35,7 @@
#include "dynamic-string.h"
#include "fatal-signal.h"
#include "packets.h"
+#include "poll-loop.h"
#include "util.h"
#include "vlog.h"
#if AF_PACKET && __linux__
@@ -889,6 +890,14 @@ xpipe(int fds[2])
}
}
+void
+xsocketpair(int domain, int type, int protocol, int fds[2])
+{
+ if (socketpair(domain, type, protocol, fds)) {
+ VLOG_FATAL("failed to create socketpair (%s)", strerror(errno));
+ }
+}
+
static int
getsockopt_int(int fd, int level, int option, const char *optname, int *valuep)
{
@@ -1048,3 +1057,249 @@ describe_fd(int fd)
}
return ds_steal_cstr(&string);
}
+
+/* Returns the total of the 'iov_len' members of the 'n_iovs' in 'iovs'.
+ * The caller must ensure that the total does not exceed SIZE_MAX. */
+size_t
+iovec_len(const struct iovec iovs[], size_t n_iovs)
+{
+ size_t len = 0;
+ size_t i;
+
+ for (i = 0; i < n_iovs; i++) {
+ len += iovs[i].iov_len;
+ }
+ return len;
+}
+
+/* Returns true if all of the 'n_iovs' iovecs in 'iovs' have length zero. */
+bool
+iovec_is_empty(const struct iovec iovs[], size_t n_iovs)
+{
+ size_t i;
+
+ for (i = 0; i < n_iovs; i++) {
+ if (iovs[i].iov_len) {
+ return false;
+ }
+ }
+ return true;
+}
+
+/* Sends the 'n_iovs' iovecs of data in 'iovs' and the 'n_fds' file descriptors
+ * in 'fds' on Unix domain socket 'sock'. Returns the number of bytes
+ * successfully sent or -1 if an error occurred. On error, sets errno
+ * appropriately. */
+int
+send_iovec_and_fds(int sock,
+ const struct iovec *iovs, size_t n_iovs,
+ const int fds[], size_t n_fds)
+{
+ assert(sock >= 0);
+ if (n_fds > 0) {
+ union {
+ struct cmsghdr cm;
+ char control[CMSG_SPACE(SOUTIL_MAX_FDS * sizeof *fds)];
+ } cmsg;
+ struct msghdr msg;
+
+ assert(!iovec_is_empty(iovs, n_iovs));
+ assert(n_fds <= SOUTIL_MAX_FDS);
+
+ memset(&cmsg, 0, sizeof cmsg);
+ cmsg.cm.cmsg_len = CMSG_LEN(n_fds * sizeof *fds);
+ cmsg.cm.cmsg_level = SOL_SOCKET;
+ cmsg.cm.cmsg_type = SCM_RIGHTS;
+ memcpy(CMSG_DATA(&cmsg.cm), fds, n_fds * sizeof *fds);
+
+ msg.msg_name = NULL;
+ msg.msg_namelen = 0;
+ msg.msg_iov = (struct iovec *) iovs;
+ msg.msg_iovlen = n_iovs;
+ msg.msg_control = &cmsg.cm;
+ msg.msg_controllen = CMSG_SPACE(n_fds * sizeof *fds);
+ msg.msg_flags = 0;
+
+ return sendmsg(sock, &msg, 0);
+ } else {
+ return writev(sock, iovs, n_iovs);
+ }
+}
+
+/* Sends the 'n_iovs' iovecs of data in 'iovs' and the 'n_fds' file descriptors
+ * in 'fds' on Unix domain socket 'sock'. If 'skip_bytes' is nonzero, then the
+ * first 'skip_bytes' of data in the iovecs are not sent, and none of the file
+ * descriptors are sent. The function continues to retry sending until an
+ * error (other than EINTR) occurs or all the data and fds are sent.
+ *
+ * Returns 0 if all the data and fds were successfully sent, otherwise a
+ * positive errno value. Regardless of success, stores the number of bytes
+ * sent (always at least 'skip_bytes') in '*bytes_sent'. (If at least one byte
+ * is sent, then all the fds have been sent.)
+ *
+ * 'skip_bytes' must be less than or equal to iovec_len(iovs, n_iovs). */
+int
+send_iovec_and_fds_fully(int sock,
+ const struct iovec iovs[], size_t n_iovs,
+ const int fds[], size_t n_fds,
+ size_t skip_bytes, size_t *bytes_sent)
+{
+ *bytes_sent = 0;
+ while (n_iovs > 0) {
+ int retval;
+
+ if (skip_bytes) {
+ retval = skip_bytes;
+ skip_bytes = 0;
+ } else if (!*bytes_sent) {
+ retval = send_iovec_and_fds(sock, iovs, n_iovs, fds, n_fds);
+ } else {
+ retval = writev(sock, iovs, n_iovs);
+ }
+
+ if (retval > 0) {
+ *bytes_sent += retval;
+ while (retval > 0) {
+ const uint8_t *base = iovs->iov_base;
+ size_t len = iovs->iov_len;
+
+ if (retval < len) {
+ size_t sent;
+ int error;
+
+ error = write_fully(sock, base + retval, len - retval,
+ &sent);
+ *bytes_sent += sent;
+ retval += sent;
+ if (error) {
+ return error;
+ }
+ }
+ retval -= len;
+ iovs++;
+ n_iovs--;
+ }
+ } else if (retval == 0) {
+ if (iovec_is_empty(iovs, n_iovs)) {
+ break;
+ }
+ VLOG_WARN("send returned 0");
+ return EPROTO;
+ } else if (errno != EINTR) {
+ return errno;
+ }
+ }
+
+ return 0;
+}
+
+/* Sends the 'n_iovs' iovecs of data in 'iovs' and the 'n_fds' file descriptors
+ * in 'fds' on Unix domain socket 'sock'. The function continues to retry
+ * sending until an error (other than EAGAIN or EINTR) occurs or all the data
+ * and fds are sent. Upon EAGAIN, the function blocks until the socket is
+ * ready for more data.
+ *
+ * Returns 0 if all the data and fds were successfully sent, otherwise a
+ * positive errno value. */
+int
+send_iovec_and_fds_fully_block(int sock,
+ const struct iovec iovs[], size_t n_iovs,
+ const int fds[], size_t n_fds)
+{
+ size_t sent = 0;
+
+ for (;;) {
+ int error;
+
+ error = send_iovec_and_fds_fully(sock, iovs, n_iovs,
+ fds, n_fds, sent, &sent);
+ if (error != EAGAIN) {
+ return error;
+ }
+ poll_fd_wait(sock, POLLOUT);
+ poll_block();
+ }
+}
+
+/* Attempts to receive from Unix domain socket 'sock' up to 'size' bytes of
+ * data into 'data' and up to SOUTIL_MAX_FDS file descriptors into 'fds'.
+ *
+ * - Upon success, returns the number of bytes of data copied into 'data'
+ * and stores the number of received file descriptors into '*n_fdsp'.
+ *
+ * - On failure, returns a negative errno value and stores 0 in
+ * '*n_fdsp'.
+ *
+ * - On EOF, returns 0 and stores 0 in '*n_fdsp'. */
+int
+recv_data_and_fds(int sock,
+ void *data, size_t size,
+ int fds[SOUTIL_MAX_FDS], size_t *n_fdsp)
+{
+ union {
+ struct cmsghdr cm;
+ char control[CMSG_SPACE(SOUTIL_MAX_FDS * sizeof *fds)];
+ } cmsg;
+ struct msghdr msg;
+ int retval;
+ struct cmsghdr *p;
+ size_t i;
+
+ *n_fdsp = 0;
+
+ do {
+ struct iovec iov;
+
+ iov.iov_base = data;
+ iov.iov_len = size;
+
+ msg.msg_name = NULL;
+ msg.msg_namelen = 0;
+ msg.msg_iov = &iov;
+ msg.msg_iovlen = 1;
+ msg.msg_control = &cmsg.cm;
+ msg.msg_controllen = sizeof cmsg.control;
+ msg.msg_flags = 0;
+
+ retval = recvmsg(sock, &msg, 0);
+ } while (retval < 0 && errno == EINTR);
+ if (retval <= 0) {
+ return retval < 0 ? -errno : 0;
+ }
+
+ for (p = CMSG_FIRSTHDR(&msg); p; p = CMSG_NXTHDR(&msg, p)) {
+ if (p->cmsg_level != SOL_SOCKET || p->cmsg_type != SCM_RIGHTS) {
+ VLOG_ERR("unexpected control message %d:%d",
+ (int) p->cmsg_level, (int) p->cmsg_type);
+ goto error;
+ } else if (*n_fdsp) {
+ VLOG_ERR("multiple SCM_RIGHTS received");
+ goto error;
+ } else {
+ size_t n_fds = (p->cmsg_len - CMSG_LEN(0)) / sizeof *fds;
+ const int *fds_data = (const int *) CMSG_DATA(p);
+
+ assert(n_fds > 0);
+ if (n_fds > SOUTIL_MAX_FDS) {
+ VLOG_ERR("%zu fds received but only %d supported",
+ n_fds, SOUTIL_MAX_FDS);
+ for (i = 0; i < n_fds; i++) {
+ close(fds_data[i]);
+ }
+ goto error;
+ }
+
+ *n_fdsp = n_fds;
+ memcpy(fds, fds_data, n_fds * sizeof *fds);
+ }
+ }
+
+ return retval;
+
+error:
+ for (i = 0; i < *n_fdsp; i++) {
+ close(fds[i]);
+ }
+ *n_fdsp = 0;
+ return EPROTO;
+}
diff --git a/lib/socket-util.h b/lib/socket-util.h
index e2e0d9a..a0e7970 100644
--- a/lib/socket-util.h
+++ b/lib/socket-util.h
@@ -71,4 +71,28 @@ char *describe_fd(int fd);
* in <netinet/ip.h> is used. */
#define DSCP_DEFAULT (IPTOS_PREC_INTERNETCONTROL >> 2)
+/* Maximum number of fds that we support sending or receiving at one time
+ * across a Unix domain socket. */
+#define SOUTIL_MAX_FDS 8
+
+/* Iovecs. */
+size_t iovec_len(const struct iovec *iovs, size_t n_iovs);
+bool iovec_is_empty(const struct iovec *iovs, size_t n_iovs);
+
+/* Functions particularly useful for Unix domain sockets. */
+void xsocketpair(int domain, int type, int protocol, int fds[2]);
+int send_iovec_and_fds(int sock,
+ const struct iovec *iovs, size_t n_iovs,
+ const int fds[], size_t n_fds);
+int send_iovec_and_fds_fully(int sock,
+ const struct iovec *iovs, size_t n_iovs,
+ const int fds[], size_t n_fds,
+ size_t skip_bytes, size_t *bytes_sent);
+int send_iovec_and_fds_fully_block(int sock,
+ const struct iovec *iovs, size_t n_iovs,
+ const int fds[], size_t n_fds);
+int recv_data_and_fds(int sock,
+ void *data, size_t size,
+ int fds[SOUTIL_MAX_FDS], size_t *n_fdsp);
+
#endif /* socket-util.h */
--
1.7.2.5
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