change the barrier so that fd's are always passed and received with

the first byte of the imsg they belong to.

idea, tweaks and ok claudio@

diff --git a/lib/libutil/imsg-buffer.c b/lib/libutil/imsg-buffer.c
index 7c60d9e..4526842 100644 (file)
--- a/lib/libutil/imsg-buffer.c
+++ b/lib/libutil/imsg-buffer.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: imsg-buffer.c,v 1.12 2019/01/20 02:50:03 bcook Exp $  */
+/*     $OpenBSD: imsg-buffer.c,v 1.13 2021/03/31 17:42:24 eric Exp $   */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -225,7 +225,7 @@ int
 msgbuf_write(struct msgbuf *msgbuf)
 {
        struct iovec     iov[IOV_MAX];
-       struct ibuf     *buf;
+       struct ibuf     *buf, *buf0 = NULL;
        unsigned int     i = 0;
        ssize_t          n;
        struct msghdr    msg;
@@ -241,24 +241,26 @@ msgbuf_write(struct msgbuf *msgbuf)
        TAILQ_FOREACH(buf, &msgbuf->bufs, entry) {
                if (i >= IOV_MAX)
                        break;
+               if (i > 0 && buf->fd != -1)
+                       break;
                iov[i].iov_base = buf->buf + buf->rpos;
                iov[i].iov_len = buf->wpos - buf->rpos;
                i++;
                if (buf->fd != -1)
-                       break;
+                       buf0 = buf;
        }
 
        msg.msg_iov = iov;
        msg.msg_iovlen = i;
 
-       if (buf != NULL && buf->fd != -1) {
+       if (buf0 != NULL) {
                msg.msg_control = (caddr_t)&cmsgbuf.buf;
                msg.msg_controllen = sizeof(cmsgbuf.buf);
                cmsg = CMSG_FIRSTHDR(&msg);
                cmsg->cmsg_len = CMSG_LEN(sizeof(int));
                cmsg->cmsg_level = SOL_SOCKET;
                cmsg->cmsg_type = SCM_RIGHTS;
-               *(int *)CMSG_DATA(cmsg) = buf->fd;
+               *(int *)CMSG_DATA(cmsg) = buf0->fd;
        }
 
 again:
@@ -279,9 +281,9 @@ again:
         * assumption: fd got sent if sendmsg sent anything
         * this works because fds are passed one at a time
         */
-       if (buf != NULL && buf->fd != -1) {
-               close(buf->fd);
-               buf->fd = -1;
+       if (buf0 != NULL) {
+               close(buf0->fd);
+               buf0->fd = -1;
        }
 
        msgbuf_drain(msgbuf, n);