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lib: Fix nondeterministic command matches in rare cases

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When a user erroneously defines two commands which can
match the same input and at least one of the tokens defined
last in the command is a selector or option, the matcher
does not detect an ambiguous match and matches the command
installed first (leftmost in the graph).

Fix is to do a full walkthrough of the follow set when
matching the final token in a command to check that there
is exactly one possible match, and to throw an ambiguity
error otherwise.

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>
This commit is contained in:
Quentin Young 2016-11-15 22:15:18 +00:00
parent fefa0d8214
commit 3c7ca60c41
1 changed files with 8 additions and 2 deletions
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10
lib/command_match.c
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@ -240,6 +240,11 @@ command_match_r (struct graph_node *start, vector vline, unsigned int n)
struct cmd_token *tok = gn->data; struct cmd_token *tok = gn->data;
if (tok->type == END_TKN) if (tok->type == END_TKN)
{ {
if (currbest) // there is more than one END_TKN in the follow set
{
ambiguous = 1;
break;
}
currbest = list_new(); currbest = list_new();
// node should have one child node with the element // node should have one child node with the element
struct graph_node *leaf = vector_slot (gn->to, 0); struct graph_node *leaf = vector_slot (gn->to, 0);
@ -251,9 +256,10 @@ command_match_r (struct graph_node *start, vector vline, unsigned int n)
struct cmd_element *el = leaf->data; struct cmd_element *el = leaf->data;
listnode_add (currbest, el); listnode_add (currbest, el);
currbest->del = (void (*)(void *)) &del_cmd_token; currbest->del = (void (*)(void *)) &del_cmd_token;
break; // do not break immediately; continue walking through the follow set
// to ensure that there is exactly one END_TKN
} }
else continue; continue;
} }
// else recurse on candidate child node // else recurse on candidate child node