Filter: Implement for loops

For loops allow to iterate over elements in compound data like BGP paths
or community lists. The syntax is:

  for [ <type> ] <variable> in <expr> do <command-body>
This commit is contained in:
Ondrej Zajicek (work) 2022-03-14 20:36:20 +01:00 committed by Ondrej Zajicek
parent 1ac8e11bba
commit cb339a3067
8 changed files with 254 additions and 8 deletions

View file

@ -1683,7 +1683,8 @@ prefix and an ASN as arguments.
<sect>Control structures
<label id="control-structures">
<p>Filters support two control structures: conditions and case switches.
<p>Filters support several control structures: conditions, for loops and case
switches.
<p>Syntax of a condition is: <cf>if <M>boolean expression</M> then <m/commandT/;
else <m/commandF/;</cf> and you can use <cf>{ <m/command1/; <m/command2/;
@ -1691,6 +1692,14 @@ else <m/commandF/;</cf> and you can use <cf>{ <m/command1/; <m/command2/;
omitted. If the <cf><m>boolean expression</m></cf> is true, <m/commandT/ is
executed, otherwise <m/commandF/ is executed.
<p>For loops allow to iterate over elements in compound data like BGP paths or
community lists. The syntax is: <cf>for [ <m/type/ ] <m/variable/ in <m/expr/
do <m/command/;</cf> and you can also use compound command like in conditions.
The expression is evaluated to a compound data, then for each element from such
data the command is executed with the item assigned to the variable. A variable
may be an existing one (when just name is used) or a locally defined (when type
and name is used). In both cases, it must have the same type as elements.
<p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case
<m/expr/ { else: | <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [
... ] }</cf>. The expression after <cf>case</cf> can be of any type which can be
@ -1703,16 +1712,21 @@ neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed.
<p>Here is example that uses <cf/if/ and <cf/case/ structures:
<code>
if 1234 = i then printn "."; else {
print "not 1234";
print "You need {} around multiple commands";
}
for int asn in bgp_path do {
printn "ASN: ", asn;
if asn < 65536 then print " (2B)"; else print " (4B)";
}
case arg1 {
2: print "two"; print "I can do more commands without {}";
3 .. 5: print "three to five";
else: print "something else";
}
if 1234 = i then printn "."; else {
print "not 1234";
print "You need {} around multiple commands";
}
</code>

View file

@ -307,6 +307,7 @@ CF_KEYWORDS(FUNCTION, PRINT, PRINTN, UNSET, RETURN,
INT, BOOL, IP, TYPE, PREFIX, RD, PAIR, QUAD, EC, LC,
SET, STRING, BGPMASK, BGPPATH, CLIST, ECLIST, LCLIST,
IF, THEN, ELSE, CASE,
FOR, IN, DO,
TRUE, FALSE, RT, RO, UNKNOWN, GENERIC,
FROM, GW, NET, MASK, PROTO, SOURCE, SCOPE, DEST, IFNAME, IFINDEX, WEIGHT, GW_MPLS,
PREFERENCE,
@ -342,6 +343,7 @@ CF_KEYWORDS(FUNCTION, PRINT, PRINTN, UNSET, RETURN,
%type <v> set_atom switch_atom fipa
%type <px> fprefix
%type <t> get_cf_position
%type <s> for_var
CF_GRAMMAR
@ -899,6 +901,11 @@ var:
$$ = f_new_inst(FI_VAR_INIT, $3, sym);
}
for_var:
type symbol { $$ = cf_define_symbol($2, SYM_VARIABLE | $1, offset, f_new_var(sym_->scope)); }
| CF_SYM_KNOWN { $$ = $1; cf_assert_symbol($1, SYM_VARIABLE); }
;
cmd:
'{' cmds_scoped '}' {
$$ = $2;
@ -909,6 +916,18 @@ cmd:
| IF term THEN cmd ELSE cmd {
$$ = f_new_inst(FI_CONDITION, $2, $4, $6);
}
| FOR {
/* Reserve space for walk data on stack */
cf_push_scope(NULL);
conf_this_scope->slots += 2;
} for_var IN
/* Parse term in the parent scope */
{ conf_this_scope->active = 0; } term { conf_this_scope->active = 1; }
DO cmd {
cf_pop_scope();
$$ = f_new_inst(FI_FOR_INIT, $6, $3);
$$->next = f_new_inst(FI_FOR_NEXT, $3, $9);
}
| CF_SYM_KNOWN '=' term ';' {
switch ($1->class) {
case SYM_VARIABLE_RANGE:

View file

@ -72,6 +72,7 @@ enum f_type
f_type_element_type(enum f_type t)
{
switch(t) {
case T_PATH: return T_INT;
case T_CLIST: return T_PAIR;
case T_ECLIST: return T_EC;
case T_LCLIST: return T_LC;

View file

@ -87,6 +87,11 @@
* m4_dnl RESULT_VOID; return undef
* m4_dnl }
*
* Note that runtime arguments m4_dnl (ARG*, VARARG) must be defined before
* parse-time arguments m4_dnl (LINE, SYMBOL, ...). During linearization,
* first ones move position in f_line by linearizing arguments first, while
* second ones store data to the current position.
*
* Also note that the { ... } blocks are not respected by M4 at all.
* If you get weird unmatched-brace-pair errors, check what it generated and why.
* What is really considered as one instruction is not the { ... } block
@ -543,6 +548,94 @@
RESULT_VAL(val);
}
INST(FI_FOR_INIT, 1, 0) {
NEVER_CONSTANT;
ARG_ANY(1);
SYMBOL;
FID_NEW_BODY()
ASSERT((sym->class & ~0xff) == SYM_VARIABLE);
/* Static type check */
if (f1->type)
{
enum f_type t_var = (sym->class & 0xff);
enum f_type t_arg = f_type_element_type(f1->type);
if (!t_arg)
cf_error("Value of expression in FOR must be iterable, got %s",
f_type_name(f1->type));
if (t_var != t_arg)
cf_error("Loop variable '%s' in FOR must be %s, is %s",
sym->name, f_type_name(t_arg), f_type_name(t_var));
}
FID_INTERPRET_BODY()
/* Dynamic type check */
if ((sym->class & 0xff) != f_type_element_type(v1.type))
runtime("Mismatched argument and variable type");
/* Setup the index */
v2 = (struct f_val) { .type = T_INT, .val.i = 0 };
/* Keep v1 and v2 on the stack */
fstk->vcnt += 2;
}
INST(FI_FOR_NEXT, 2, 0) {
NEVER_CONSTANT;
SYMBOL;
/* Type checks are done in FI_FOR_INIT */
/* Loop variable */
struct f_val *var = &fstk->vstk[curline.vbase + sym->offset];
int step = 0;
switch(v1.type)
{
case T_PATH:
var->type = T_INT;
step = as_path_walk(v1.val.ad, &v2.val.i, &var->val.i);
break;
case T_CLIST:
var->type = T_PAIR;
step = int_set_walk(v1.val.ad, &v2.val.i, &var->val.i);
break;
case T_ECLIST:
var->type = T_EC;
step = ec_set_walk(v1.val.ad, &v2.val.i, &var->val.ec);
break;
case T_LCLIST:
var->type = T_LC;
step = lc_set_walk(v1.val.ad, &v2.val.i, &var->val.lc);
break;
default:
runtime( "Clist or lclist expected" );
}
if (step)
{
/* Keep v1 and v2 on the stack */
fstk->vcnt += 2;
/* Repeat this instruction */
curline.pos--;
/* Execute the loop body */
LINE(1, 0);
/* Space for loop variable, may be unused */
fstk->vcnt += 1;
}
else
var->type = T_VOID;
}
INST(FI_CONDITION, 1, 0) {
ARG(1, T_BOOL);
if (v1.val.i)

View file

@ -758,6 +758,15 @@ int set set12;
bt_assert(delete(p2, [4..5]) = prepend(prepend(prepend(prepend(+empty+, 3), 3), 2), 1));
bt_assert(format([= 1 2+ 3 =]) = "[= 1 2 + 3 =]");
# iteration over path
int x = 0;
int y = 0;
for int i in p2 do {
x = x + i;
y = y + x;
}
bt_assert(x = 18 && y = 50);
}
bt_test_suite(t_path, "Testing paths");
@ -884,6 +893,12 @@ clist r;
bt_assert(format(r) = "(clist (2,1) (1,3) (2,2) (3,1) (2,3))");
bt_assert(r.min = (1,3));
bt_assert(r.max = (3,1));
# iteration over clist
int x = 0;
for pair c in r do
x = x + c.asn * c.asn * c.data;
bt_assert(x = 36);
}
bt_test_suite(t_clist, "Testing lists of communities");
@ -999,6 +1014,13 @@ eclist r;
bt_assert(format(r) = "(eclist (rt, 2, 1) (rt, 1, 3) (rt, 2, 2) (rt, 3, 1) (rt, 2, 3))");
bt_assert(r.min = (rt, 1, 3));
bt_assert(r.max = (rt, 3, 1));
# iteration over eclist
int x = 0;
for ec c in r do
if c > (rt, 2, 0) && c < (rt, 3, 0) then
x = x + 1;
bt_assert(x = 3);
}
bt_test_suite(t_eclist, "Testing lists of extended communities");
@ -1117,6 +1139,19 @@ lclist r;
bt_assert(format(r) = "(lclist (2, 3, 3) (1, 2, 3) (2, 3, 1) (3, 1, 2) (2, 1, 3))");
bt_assert(r.min = (1, 2, 3));
bt_assert(r.max = (3, 1, 2));
# iteration over lclist
int x = 0;
int y = 0;
lc mx = (0, 0, 0);
for lc c in r do {
int asn2 = c.asn * c.asn;
x = x + asn2 * c.data1;
y = y + asn2 * c.data2;
if c > mx then mx = c;
}
bt_assert(x = 39 && y = 49);
bt_assert(mx = r.max);
}
bt_test_suite(t_lclist, "Testing lists of large communities");
@ -1580,13 +1615,16 @@ filter vpn_filter
bt_assert(net.type != NET_IP6);
bt_assert(net.rd = 0:1:2);
bool b = false;
case (net.type) {
NET_IP4: print "IPV4";
NET_IP6: print "IPV6";
else: b = true;
}
bt_assert(b);
bt_check_assign(from, 10.20.30.40);
bt_check_assign(gw, 55.55.55.44);
# bt_check_assign(gw, 55.55.55.44);
bgp_community.add((3,5));
bgp_ext_community.add((ro, 135, 999));

View file

@ -669,6 +669,35 @@ as_path_filter(struct linpool *pool, const struct adata *path, const struct f_va
return res;
}
int
as_path_walk(const struct adata *path, uint *pos, uint *val)
{
if (!path)
return 0;
const u8 *p = path->data;
const u8 *q = p + path->length;
uint n, x = *pos;
while (p < q)
{
n = p[1];
p += 2;
if (x < n)
{
*val = get_as(p + x * BS);
*pos += 1;
return 1;
}
p += n * BS;
x -= n;
}
return 0;
}
struct pm_pos
{

View file

@ -693,3 +693,51 @@ lc_set_max(const struct adata *list, lcomm *val)
*val = (lcomm) { res[0], res[1], res[2] };
return 1;
}
int
int_set_walk(const struct adata *list, uint *pos, uint *val)
{
if (!list)
return 0;
if (*pos >= (uint) int_set_get_size(list))
return 0;
u32 *res = int_set_get_data(list) + *pos;
*val = *res;
*pos += 1;
return 1;
}
int
ec_set_walk(const struct adata *list, uint *pos, u64 *val)
{
if (!list)
return 0;
if (*pos >= (uint) int_set_get_size(list))
return 0;
u32 *res = int_set_get_data(list) + *pos;
*val = ec_generic(res[0], res[1]);
*pos += 2;
return 1;
}
int
lc_set_walk(const struct adata *list, uint *pos, lcomm *val)
{
if (!list)
return 0;
if (*pos >= (uint) int_set_get_size(list))
return 0;
u32 *res = int_set_get_data(list) + *pos;
*val = (lcomm) { res[0], res[1], res[2] };
*pos += 3;
return 1;
}

View file

@ -51,6 +51,7 @@ u32 as_path_get_last_nonaggregated(const struct adata *path);
int as_path_contains(const struct adata *path, u32 as, int min);
int as_path_match_set(const struct adata *path, const struct f_tree *set);
const struct adata *as_path_filter(struct linpool *pool, const struct adata *path, const struct f_val *set, int pos);
int as_path_walk(const struct adata *path, uint *pos, uint *val);
static inline struct adata *as_path_prepend(struct linpool *pool, const struct adata *path, u32 as)
{ return as_path_prepend2(pool, path, AS_PATH_SEQUENCE, as); }
@ -225,6 +226,9 @@ int lc_set_min(const struct adata *list, lcomm *val);
int int_set_max(const struct adata *list, u32 *val);
int ec_set_max(const struct adata *list, u64 *val);
int lc_set_max(const struct adata *list, lcomm *val);
int int_set_walk(const struct adata *list, uint *pos, u32 *val);
int ec_set_walk(const struct adata *list, uint *pos, u64 *val);
int lc_set_walk(const struct adata *list, uint *pos, lcomm *val);
void ec_set_sort_x(struct adata *set); /* Sort in place */