From 430636328c2fbd9fffc0eac5114462c200b7f2cb Mon Sep 17 00:00:00 2001
From: Neels Hofmeyr <neels@hofmeyr.de>
Date: Tue, 19 Sep 2017 23:54:01 +0200
Subject: fix vty regression: empty parent node

The recent exit-by-indent patch breaks a VTY case where a node is entered but
directly followed by a sibling or ancestor without listing any child nodes.
Regression introduced by I24cbb3f6de111f2d31110c3c484c066f1153aac9.

An example is a common usage in osmo-bts, where 'phy N' / 'instance N' is a
parent node that is commonly left empty:

	phy 0
	 instance 0
	bts 0
	 band 1800

Before this patch, this case produces the error:

	There is no such command.
	Error occurred during reading the below line:
	bts 0

Fix indentation parsing logic in command.c to accomodate this case.

Add a unit test for empty parent node.

Change-Id: Ia0880a17ae55accb092ae8585cc3a1bec9986891
---
 src/vty/command.c             | 39 ++++++++++++++++++++++++++++++++-------
 tests/Makefile.am             |  1 +
 tests/vty/ok_empty_parent.cfg |  2 ++
 tests/vty/vty_test.c          |  1 +
 tests/vty/vty_test.ok         |  2 ++
 5 files changed, 38 insertions(+), 7 deletions(-)
 create mode 100644 tests/vty/ok_empty_parent.cfg

diff --git a/src/vty/command.c b/src/vty/command.c
index a65b4de5..46c9fa28 100644
--- a/src/vty/command.c
+++ b/src/vty/command.c
@@ -2374,14 +2374,39 @@ int config_from_file(struct vty *vty, FILE * fp)
 			continue;
 		}
 
-		/* We have a nonempty line. This might be the first on a deeper indenting level, so let's
-		 * remember this indent if we don't have one yet. */
-		if (!vty->indent)
-			vty->indent = talloc_strdup(vty, indent);
+		/* We have a nonempty line. */
+		if (!vty->indent) {
+			/* We have just entered a node and expecting the first child to come up; but we
+			 * may also skip right back to a parent or ancestor level. */
+			parent = vty_parent(vty);
 
-		cmp = indent_cmp(indent, vty->indent);
-		if (cmp == EINVAL)
-			goto return_invalid_indent;
+			/* If there is no parent, record any indentation we encounter. */
+			cmp = parent ? indent_cmp(indent, parent->indent) : 1;
+
+			if (cmp == EINVAL)
+				goto return_invalid_indent;
+
+			if (cmp <= 0) {
+				/* We have gone right back to the parent level or higher, we are skipping
+				 * this child node level entirely. Pop the parent to go back to a node
+				 * that was actually there (to reinstate vty->indent) and re-use below
+				 * go-parent while-loop to find an accurate match of indent in the node
+				 * ancestry. */
+				vty_go_parent(vty);
+			} else {
+				/* The indent is deeper than the just entered parent, record the new
+				 * indentation characters. */
+				vty->indent = talloc_strdup(vty, indent);
+				/* This *is* the new indentation. */
+				cmp = 0;
+			}
+		} else {
+			/* There is a known indentation for this node level, validate and detect node
+			 * exits. */
+			cmp = indent_cmp(indent, vty->indent);
+			if (cmp == EINVAL)
+				goto return_invalid_indent;
+		}
 
 		/* Less indent: go up the parent nodes to find matching amount of less indent. When this
 		 * loop exits, we want to have found an exact match, i.e. cmp == 0. */
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 8935bf72..b1387174 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -222,6 +222,7 @@ EXTRA_DIST = testsuite.at $(srcdir)/package.m4 $(TESTSUITE)		\
 	     vty/fail_tabs_and_spaces.cfg \
 	     vty/fail_too_much_indent.cfg \
 	     vty/ok.cfg \
+	     vty/ok_empty_parent.cfg \
 	     vty/ok_ignore_blank.cfg \
 	     vty/ok_ignore_comment.cfg \
 	     vty/ok_indented_root.cfg \
diff --git a/tests/vty/ok_empty_parent.cfg b/tests/vty/ok_empty_parent.cfg
new file mode 100644
index 00000000..fe04fcfa
--- /dev/null
+++ b/tests/vty/ok_empty_parent.cfg
@@ -0,0 +1,2 @@
+line vty
+log stderr
diff --git a/tests/vty/vty_test.c b/tests/vty/vty_test.c
index eba9995c..d9af6aee 100644
--- a/tests/vty/vty_test.c
+++ b/tests/vty/vty_test.c
@@ -342,6 +342,7 @@ int main(int argc, char **argv)
 	test_exit_by_indent("fail_too_much_indent.cfg", -EINVAL);
 	test_exit_by_indent("fail_tabs_and_spaces.cfg", -EINVAL);
 	test_exit_by_indent("ok_indented_root.cfg", 0);
+	test_exit_by_indent("ok_empty_parent.cfg", 0);
 
 	/* Leak check */
 	OSMO_ASSERT(talloc_total_blocks(stats_ctx) == 1);
diff --git a/tests/vty/vty_test.ok b/tests/vty/vty_test.ok
index b2df1a11..f9fea34d 100644
--- a/tests/vty/vty_test.ok
+++ b/tests/vty/vty_test.ok
@@ -128,4 +128,6 @@ reading file fail_tabs_and_spaces.cfg, expecting rc=-22
 got rc=-22
 reading file ok_indented_root.cfg, expecting rc=0
 got rc=0
+reading file ok_empty_parent.cfg, expecting rc=0
+got rc=0
 All tests passed
-- 
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