[Libguestfs] [nbdkit PATCH] server: Reinstate limited use of -e/-exportname.
Eric Blake
eblake at redhat.com
Wed Jul 22 17:58:07 UTC 2020
While we are unlikely to change our decision that -e should not
control our response to NBD_OPT_LIST (because we intend to add a new
callback .extents_list for that), it turns out that it is a lot easier
to write:
nbdkit -U - -e foo info --run 'nbdsh -u "$uri" -c "print(h.pread(3, 0))"'
than it is to write the equivalent:
nbdkit -U - info --run 'nbdsh -u nbd+unix:///foo\?socket=$unixsocket \
-c "print(h.pread(3, 0))"'
and our test-long-name.sh was evidence of that fact.
Let's revert that part of the patch, but improve the documentation to
mention that -e is now useful _only_ with --run, and only if the
client uses it.
This partially reverts commit e71178e9b71403, although for -Wshadow
reasons, we now have to name the global variable export_name due to
other code in the meantime using parameters named exportname.
Signed-off-by: Eric Blake <eblake at redhat.com>
---
docs/nbdkit-captive.pod | 12 +++++++++++-
docs/nbdkit-protocol.pod | 2 +-
docs/nbdkit.pod | 18 ++++++++++++++++++
docs/synopsis.txt | 3 ++-
server/internal.h | 1 +
server/captive.c | 20 +++++++++++++++++---
server/main.c | 3 ++-
tests/test-long-name.sh | 10 +++++-----
8 files changed, 57 insertions(+), 12 deletions(-)
diff --git a/docs/nbdkit-captive.pod b/docs/nbdkit-captive.pod
index f1ac9fc4..94e79c59 100644
--- a/docs/nbdkit-captive.pod
+++ b/docs/nbdkit-captive.pod
@@ -53,7 +53,9 @@ The following shell variables are available in the I<--run> argument:
A URI that refers to the nbdkit port or socket in the preferred form
documented by the NBD project. As this variable may contain a bare
C<?> for Unix sockets, it is safest to use $uri within double quotes
-to avoid unintentional globbing.
+to avoid unintentional globbing. For plugins that support distinct
+data based on export names, the B<-e> option to nbdkit controls which
+export name will be set in the URI.
=item C<$nbd>
@@ -72,6 +74,14 @@ If E<ne> "", the port number that nbdkit is listening on.
If E<ne> "", the Unix domain socket that nbdkit is listening on.
+=item C<$exportname>
+
+The export name (which may be "") that the process should use when
+connecting to nbdkit, as set by the B<-e> (B<--exportname>) command
+line option of nbdkit. This only matters to plugins that
+differentiate what they serve based on the export name requested by
+the client.
+
=back
I<--run> implies I<--foreground>. It is not possible, and probably
diff --git a/docs/nbdkit-protocol.pod b/docs/nbdkit-protocol.pod
index e0e4042b..8fe8c67e 100644
--- a/docs/nbdkit-protocol.pod
+++ b/docs/nbdkit-protocol.pod
@@ -102,7 +102,7 @@ Partially supported in nbdkit E<ge> 1.1.12. Support for plugins to
read the client export name added in nbdkit E<ge> 1.15.2.
Versions of nbdkit before 1.16 could advertise a single export name to
-clients, specified through the now deprecated I<-e> option. In nbdkit
+clients, via a now deprecated side effect of the I<-e> option. In nbdkit
1.15.2, plugins could read the client requested export name using
C<nbdkit_export_name()> and serve different content.
diff --git a/docs/nbdkit.pod b/docs/nbdkit.pod
index b204709b..e23cc90f 100644
--- a/docs/nbdkit.pod
+++ b/docs/nbdkit.pod
@@ -214,6 +214,24 @@ An alternative to this is L<nbdkit-captive(1)/CAPTIVE NBDKIT>.
This option implies I<--foreground>.
+=item B<-e> EXPORTNAME
+
+=item B<--export> EXPORTNAME
+
+=item B<--export-name> EXPORTNAME
+
+=item B<--exportname> EXPORTNAME
+
+Set a preferred exportname to expose in the shell environment created
+during B<--run>. The use of this option without B<--run> has no
+effect. This option does I<not> change what nbdkit advertises as a
+server, but can aid in writing a captive client that wants to access
+particular content from a plugin that differentiates content based on
+the client's choice of export name.
+
+If not set, the B<--run> environment is set to access the default
+exportname C<""> (empty string).
+
=item B<-f>
=item B<--foreground>
diff --git a/docs/synopsis.txt b/docs/synopsis.txt
index caf49922..07b9dcff 100644
--- a/docs/synopsis.txt
+++ b/docs/synopsis.txt
@@ -1,4 +1,5 @@
-nbdkit [-D|--debug PLUGIN|FILTER|nbdkit.FLAG=N] [--exit-with-parent]
+nbdkit [-D|--debug PLUGIN|FILTER|nbdkit.FLAG=N]
+ [-e|--exportname EXPORTNAME] [--exit-with-parent]
[--filter FILTER ...] [-f|--foreground]
[-g|--group GROUP] [-i|--ipaddr IPADDR]
[--log stderr|syslog|null]
diff --git a/server/internal.h b/server/internal.h
index 4911a49b..1acbbb06 100644
--- a/server/internal.h
+++ b/server/internal.h
@@ -108,6 +108,7 @@ enum log_to {
};
extern struct debug_flag *debug_flags;
+extern const char *export_name;
extern bool foreground;
extern const char *ipaddr;
extern enum log_to log_to;
diff --git a/server/captive.c b/server/captive.c
index 53b82782..a8947d7c 100644
--- a/server/captive.c
+++ b/server/captive.c
@@ -61,6 +61,9 @@ run_command (void)
if (!run)
return;
+ if (!export_name)
+ export_name = "";
+
fp = open_memstream (&cmd, &len);
if (fp == NULL) {
perror ("open_memstream");
@@ -72,15 +75,26 @@ run_command (void)
if (port) {
fprintf (fp, "nbd://localhost:");
shell_quote (port, fp);
+ if (strcmp (export_name, "") != 0) {
+ putc ('/', fp);
+ uri_quote (export_name, fp);
+ }
}
else if (unixsocket) {
- fprintf (fp, "nbd+unix://\\?socket=");
+ fprintf (fp, "nbd+unix://");
+ if (strcmp (export_name, "") != 0) {
+ putc ('/', fp);
+ uri_quote (export_name, fp);
+ }
+ fprintf (fp, "\\?socket=");
uri_quote (unixsocket, fp);
}
putc ('\n', fp);
- /* $exportname is for backwards compatibility. */
- fprintf (fp, "exportname=\n");
+ /* Expose $exportname. */
+ fprintf (fp, "exportname=");
+ shell_quote (export_name, fp);
+ putc ('\n', fp);
/* Construct older $nbd "URL". Unfortunately guestfish and qemu take
* different syntax, so try to guess which one we need.
diff --git a/server/main.c b/server/main.c
index d815fe12..2f0aaf07 100644
--- a/server/main.c
+++ b/server/main.c
@@ -79,6 +79,7 @@ static bool is_config_key (const char *key, size_t len);
struct debug_flag *debug_flags; /* -D */
bool exit_with_parent; /* --exit-with-parent */
+const char *export_name; /* -e */
bool foreground; /* -f */
const char *ipaddr; /* -i */
enum log_to log_to = LOG_TO_DEFAULT; /* --log */
@@ -344,7 +345,7 @@ main (int argc, char *argv[])
break;
case 'e':
- /* Does nothing, ignored for compatibility with older nbdkit. */
+ export_name = optarg;
break;
case 'f':
diff --git a/tests/test-long-name.sh b/tests/test-long-name.sh
index 1da2515a..897f8e94 100755
--- a/tests/test-long-name.sh
+++ b/tests/test-long-name.sh
@@ -1,6 +1,6 @@
#!/usr/bin/env bash
# nbdkit
-# Copyright (C) 2019 Red Hat Inc.
+# Copyright (C) 2019-2020 Red Hat Inc.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
@@ -53,10 +53,6 @@ name1k=$name256$name256$name256$name256
name4k=$name1k$name1k$name1k$name1k
almost4k=${name4k%8$name16}
-# Test behavior of -e: accept 4k max, reject longer
-nbdkit -U - -e $name4k null --run true || fail=1
-nbdkit -U - -e a$name4k null --run true && fail=1
-
# Test that $exportname and $uri reflect the name
out=$(nbdkit -U - -e $name4k null --run 'echo $exportname')
if test "$name4k" != "$out"; then
@@ -110,6 +106,9 @@ assert h.get_size() == 0
EOF
'
+# TODO when we add .list_extents, we should test a plugin advertising
+# a name near 4k in length. nbdkit -e no longer does this
+if false; then
# The rest of this test uses the ‘qemu-nbd --list’ option added in qemu 4.0.
if ! qemu-nbd --help | grep -sq -- --list; then
echo "$0: skipping because qemu-nbd does not support the --list option"
@@ -118,5 +117,6 @@ fi
# Test response to NBD_OPT_LIST
nbdkit -U - -e $name4k null --run 'qemu-nbd --list -k $unixsocket' || fail=1
+fi
exit $fail
--
2.27.0
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