More files related to user-level file servers.

Also add acme!

src/lib9/sendfd.c

@@ -0,0 +1,79 @@
+#include <u.h>
+#define NOPLAN9DEFINES
+#include <libc.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+#include <unistd.h>
+#include <errno.h>
+
+typedef struct Sendfd Sendfd;
+struct Sendfd {
+	struct cmsghdr cmsg;
+	int fd;
+};
+
+int
+sendfd(int s, int fd)
+{
+	char buf[1];
+	struct iovec iov;
+	struct msghdr msg;
+	int n;
+	Sendfd sfd;
+
+	buf[0] = 0;
+	iov.iov_base = buf;
+	iov.iov_len = 1;
+
+	memset(&msg, 0, sizeof msg);
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+
+	sfd.cmsg.cmsg_len = sizeof sfd;
+	sfd.cmsg.cmsg_level = SOL_SOCKET;
+	sfd.cmsg.cmsg_type = SCM_RIGHTS;
+	sfd.fd = fd;
+
+	msg.msg_control = &sfd;
+	msg.msg_controllen = sizeof sfd;
+
+	if((n=sendmsg(s, &msg, 0)) != iov.iov_len)
+		return -1;
+	return 0;
+}
+
+int
+recvfd(int s)
+{
+	int n;
+	char buf[1];
+	struct iovec iov;
+	struct msghdr msg;
+	Sendfd sfd;
+
+	iov.iov_base = buf;
+	iov.iov_len = 1;
+
+	memset(&msg, 0, sizeof msg);
+	msg.msg_name = 0;
+	msg.msg_namelen = 0;
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+
+	memset(&sfd, 0, sizeof sfd);
+	sfd.fd = -1;
+	sfd.cmsg.cmsg_len = sizeof sfd;
+	sfd.cmsg.cmsg_level = SOL_SOCKET;
+	sfd.cmsg.cmsg_type = SCM_RIGHTS;
+
+	msg.msg_control = &sfd;
+	msg.msg_controllen = sizeof sfd;
+
+	if((n=recvmsg(s, &msg, 0)) < 0)
+		return -1;
+	if(n==0 && sfd.fd==-1){
+		werrstr("eof in recvfd");
+		return -1;
+	}
+	return sfd.fd;
+}