bird/nest/a-path.c

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/*
* BIRD -- Path Operations
*
* (c) 2000 Martin Mares <mj@ucw.cz>
* (c) 2000 Pavel Machek <pavel@ucw.cz>
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
#include "nest/bird.h"
#include "nest/route.h"
#include "nest/attrs.h"
#include "lib/resource.h"
#include "lib/unaligned.h"
#include "lib/string.h"
/* Global AS4 support, shared by all BGP instances.
* This specifies whether BA_AS_PATH attributes contain 2 or 4 B per ASN
*/
int bgp_as4_support = 1;
static void
put_as(byte *data, u32 as)
{
if (bgp_as4_support)
put_u32(data, as);
else if (as <= 0xFFFF)
put_u16(data, as);
else
bug("put_as: Try to put 32bit AS to 16bit AS Path");
}
static inline u32
get_as(byte *data)
{
return bgp_as4_support ? get_u32(data) : get_u16(data);
}
struct adata *
as_path_prepend(struct linpool *pool, struct adata *olda, u32 as)
{
int bs = bgp_as4_support ? 4 : 2;
struct adata *newa;
if (olda->length && olda->data[0] == AS_PATH_SEQUENCE && olda->data[1] < 255)
/* Starting with sequence => just prepend the AS number */
{
int nl = olda->length + bs;
newa = lp_alloc(pool, sizeof(struct adata) + nl);
newa->length = nl;
newa->data[0] = AS_PATH_SEQUENCE;
newa->data[1] = olda->data[1] + 1;
memcpy(newa->data + bs + 2, olda->data + 2, olda->length - 2);
}
else /* Create new path segment */
{
int nl = olda->length + bs + 2;
newa = lp_alloc(pool, sizeof(struct adata) + nl);
newa->length = nl;
newa->data[0] = AS_PATH_SEQUENCE;
newa->data[1] = 1;
memcpy(newa->data + bs + 2, olda->data, olda->length);
}
put_as(newa->data + 2, as);
return newa;
}
int
as_path_convert_to_old(struct adata *path, byte *dst, int *new_used)
{
byte *src = path->data;
byte *src_end = src + path->length;
byte *dst_start = dst;
u32 as;
int i, n;
*new_used = 0;
while (src < src_end)
{
n = src[1];
*dst++ = *src++;
*dst++ = *src++;
for(i=0; i<n; i++)
{
as = get_u32(src);
if (as > 0xFFFF)
{
as = AS_TRANS;
*new_used = 1;
}
put_u16(dst, as);
src += 4;
dst += 2;
}
}
return dst - dst_start;
}
int
as_path_convert_to_new(struct adata *path, byte *dst, int req_as)
{
byte *src = path->data;
byte *src_end = src + path->length;
byte *dst_start = dst;
u32 as;
int i, t, n;
while ((src < src_end) && (req_as > 0))
{
t = *src++;
n = *src++;
if (t == AS_PATH_SEQUENCE)
{
if (n > req_as)
n = req_as;
req_as -= n;
}
else // t == AS_PATH_SET
req_as--;
*dst++ = t;
*dst++ = n;
for(i=0; i<n; i++)
{
as = get_u16(src);
put_u32(dst, as);
src += 2;
dst += 4;
}
}
return dst - dst_start;
}
void
as_path_format(struct adata *path, byte *buf, unsigned int size)
{
int bs = bgp_as4_support ? 4 : 2;
byte *p = path->data;
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byte *e = p + path->length;
byte *end = buf + size - 16;
int sp = 1;
int l, isset;
while (p < e)
{
if (buf > end)
{
strcpy(buf, " ...");
return;
}
isset = (*p++ == AS_PATH_SET);
l = *p++;
if (isset)
{
if (!sp)
*buf++ = ' ';
*buf++ = '{';
sp = 0;
}
while (l-- && buf <= end)
{
if (!sp)
*buf++ = ' ';
buf += bsprintf(buf, "%u", get_as(p));
p += bs;
sp = 0;
}
if (isset)
{
*buf++ = ' ';
*buf++ = '}';
sp = 0;
}
}
*buf = 0;
}
int
as_path_getlen(struct adata *path)
{
int bs = bgp_as4_support ? 4 : 2;
int res = 0;
u8 *p = path->data;
u8 *q = p+path->length;
int len;
while (p<q)
{
switch (*p++)
{
case AS_PATH_SET: len = *p++; res++; p += bs * len; break;
case AS_PATH_SEQUENCE: len = *p++; res += len; p += bs * len; break;
default: bug("as_path_getlen: Invalid path segment");
}
}
return res;
}
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int
as_path_get_first(struct adata *path, u32 *orig_as)
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{
int bs = bgp_as4_support ? 4 : 2;
int found = 0;
u32 res = 0;
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u8 *p = path->data;
u8 *q = p+path->length;
int len;
while (p<q)
{
switch (*p++)
{
case AS_PATH_SET:
if (len = *p++)
{
found = 1;
res = get_as(p);
p += bs * len;
}
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break;
case AS_PATH_SEQUENCE:
if (len = *p++)
{
found = 1;
res = get_as(p + bs * (len - 1));
p += bs * len;
}
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break;
default: bug("as_path_get_first: Invalid path segment");
}
}
*orig_as = res;
return found;
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}
int
as_path_get_last(struct adata *path, u32 *last_as)
{
u8 *p = path->data;
if ((path->length == 0) || (p[0] != AS_PATH_SEQUENCE) || (p[1] == 0))
return 0;
else
{
*last_as = get_as(p+2);
return 1;
}
}
int
as_path_is_member(struct adata *path, u32 as)
{
int bs = bgp_as4_support ? 4 : 2;
u8 *p = path->data;
u8 *q = p+path->length;
int i, n;
while (p<q)
{
n = p[1];
p += 2;
for(i=0; i<n; i++)
{
if (get_as(p) == as)
return 1;
p += bs;
}
}
return 0;
}
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#define MASK_PLUS do { mask = mask->next; if (!mask) return next == q; \
asterisk = mask->any; \
if (asterisk) { mask = mask->next; if (!mask) { return 1; } } \
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} while(0)
int
as_path_match(struct adata *path, struct f_path_mask *mask)
{
int bs = bgp_as4_support ? 4 : 2;
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int i;
int asterisk = 0;
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u8 *p = path->data;
u8 *q = p+path->length;
int len;
u8 *next;
u32 as;
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asterisk = mask->any;
if (asterisk)
{ mask = mask->next; if (!mask) return 1; }
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while (p<q) {
switch (*p++) {
case AS_PATH_SET:
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len = *p++;
{
u8 *p_save = p;
next = p_save + bs * len;
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retry:
p = p_save;
for (i=0; i<len; i++) {
as = get_as(p);
if (asterisk && (as == mask->val)) {
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MASK_PLUS;
goto retry;
}
if (!asterisk && (as == mask->val)) {
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p = next;
MASK_PLUS;
goto okay;
}
p += bs;
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}
if (!asterisk)
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return 0;
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okay: ;
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}
break;
case AS_PATH_SEQUENCE:
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len = *p++;
for (i=0; i<len; i++) {
as = get_as(p);
if (asterisk && (as == mask->val))
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MASK_PLUS;
else if (!asterisk) {
if (as != mask->val)
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return 0;
MASK_PLUS;
}
p += bs;
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}
break;
default:
bug("as_path_match: Invalid path component");
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}
}
return 0;
}
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