[Xen-devel] [RFC PATCH 15/17] xenconsoled: add support for non-pty output

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

Handle 'output' xenstore entry, as qemu does. Right now support only few
simple options:
 - "pty" (unchanged)
 - "file:path" (overwrite file)
 - "pipe:path" (read-write file/pipe)
 - "null"

Also, when ever read() returns 0, stop reading from that source, instead
of spinning in a loop.
For now, in case of reconnect, intentionally use pty (ignore 'output'
xenstore entry), as for normal files close+open can be harmful
(especially with O_TRUNC).
---
According to qemu docs, "pipe" should behave differently - it should
open two pipes, with ".in" and ".out". According to actual qemu code, it
does that, but if it fails it fallbacks to just one file. And libxl
relies on that fallback, so I've implemented that version only.
If xenconsoled would have some man page, I'd add it there...
---
 tools/console/daemon/io.c | 62 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 57 insertions(+), 5 deletions(-)

diff --git a/tools/console/daemon/io.c b/tools/console/daemon/io.c
index 508bc2c..7afff99 100644
--- a/tools/console/daemon/io.c
+++ b/tools/console/daemon/io.c
@@ -95,6 +95,8 @@ struct console {
        int master_fd;
        int master_pollfd_idx;
        int slave_fd;
+       bool master_fd_can_read;
+       bool master_fd_can_write;
        int log_fd;
        struct buffer buffer;
        char *xspath;
@@ -705,6 +707,53 @@ static void console_unmap_interface(struct console *con)
        con->ring_ref = -1;
 }
 
+static int create_console_output(struct console *con)
+{
+       int err;
+       char *output, *path;
+
+       if (asprintf(&path, "%s/%s", con->xspath, "output") == -1) {
+               err = ENOMEM;
+               goto out;
+       }
+
+       con->master_fd_can_read = true;
+       con->master_fd_can_write = true;
+
+       output = xs_read(xs, XBT_NULL, path, NULL);
+
+       if (!output || !strcmp(output, "pty")) {
+               if (!console_create_tty(con)) {
+                       err = errno;
+                       goto out;
+               }
+       } else if (!strncmp(output, "file:", 5)) {
+               con->master_fd = open(output+5, O_WRONLY | O_CREAT | O_TRUNC, 
0600);
+               if (con->master_fd == -1) {
+                       err = errno;
+                       goto out;
+               }
+               /* this is write-only file */
+               con->master_fd_can_read = false;
+       } else if (!strncmp(output, "pipe:", 5)) {
+               con->master_fd = open(output+5, O_RDWR);
+               if (con->master_fd == -1) {
+                       err = errno;
+                       goto out;
+               }
+       } else if (!strcmp(output, "null")) {
+               con->master_fd = open("/dev/null", O_RDWR);
+               if (con->master_fd == -1) {
+                       err = errno;
+                       goto out;
+               }
+       }
+
+       err = 0;
+out:
+       return err;
+}
+
 static int console_create_ring(struct console *con)
 {
        int err, remote_port, ring_ref, rc;
@@ -800,10 +849,9 @@ static int console_create_ring(struct console *con)
        con->remote_port = remote_port;
 
        if (con->master_fd == -1) {
-               if (!console_create_tty(con)) {
-                       err = errno;
+               err = create_console_output(con);
+               if (err)
                        goto err_xce;
-               }
        }
 
        if (log_guest && (con->log_fd == -1))
@@ -916,6 +964,8 @@ static int console_init(struct console *con, struct domain 
*dom, void **data)
 
        con->master_fd = -1;
        con->master_pollfd_idx = -1;
+       con->master_fd_can_read = true;
+       con->master_fd_can_write = true;
        con->slave_fd = -1;
        con->log_fd = -1;
        con->ring_ref = -1;
@@ -1127,6 +1177,8 @@ static void handle_tty_read(struct console *con)
         */
        if (len < 0) {
                console_handle_broken_tty(con, domain_is_valid(dom->domid));
+       } else if (len == 0) {
+               con->master_fd_can_read = false;
        } else if (domain_is_valid(dom->domid)) {
                prod = intf->in_prod;
                for (i = 0; i < len; i++) {
@@ -1371,10 +1423,10 @@ static void maybe_add_console_tty_fd(struct console 
*con)
 {
        if (con->master_fd != -1) {
                short events = 0;
-               if (!con->d->is_dead && ring_free_bytes(con))
+               if (!con->d->is_dead && con->master_fd_can_read && 
ring_free_bytes(con))
                        events |= POLLIN;
 
-               if (!buffer_empty(&con->buffer))
+               if (con->master_fd_can_write && !buffer_empty(&con->buffer))
                        events |= POLLOUT;
 
                if (events)
-- 
git-series 0.9.1

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