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BGP: Implement extended optional parameters length

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Extends BGP options/capabilities data length to 16bit, to avoid issues
with too many capabilities. See draft-ietf-idr-ext-opt-param-07
This commit is contained in:
Ondrej Zajicek (work) 2019-08-20 19:12:59 +02:00
parent a297a4f044
commit 524d253853
3 changed files with 71 additions and 23 deletions
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2
lib/birdlib.h
View file

@ -38,7 +38,7 @@ struct align_probe { char x; long int y; };
#define ARRAY_SIZE(a) (sizeof(a)/sizeof(*(a)))
#define BYTES(n) ((((uint) (n)) + 7) / 8)
#define CALL(fn, args...) ({ if (fn) fn(args); })
#define ADVANCE(w, r, l) ({ r -= l; w += l; })
#define ADVANCE(w, r, l) ({ r -= (l); w += (l); })
static inline int uint_cmp(uint i1, uint i2)
{ return (int)(i1 > i2) - (int)(i1 < i2); }

1
proto/bgp/bgp.c
View file

@ -100,6 +100,7 @@
* RFC 8203 - BGP Administrative Shutdown Communication
* RFC 8212 - Default EBGP Route Propagation Behavior without Policies
* draft-ietf-idr-bgp-extended-messages-27
* draft-ietf-idr-ext-opt-param-07
* draft-uttaro-idr-bgp-persistence-04
*/

91
proto/bgp/packets.c
View file

@ -294,8 +294,8 @@ bgp_write_capabilities(struct bgp_conn *conn, byte *buf)
/*
* Note that max length is ~ 22+21*af_count. With max 12 channels that is
* 274. Option limit is 253 and buffer size is 4096, so we cannot overflow
* unless we add new capabilities or more AFs. XXXXX
* 274. We are limited just by buffer size (4096, minus header), as we support
* extended optional parameres. Therefore, we have enough space for expansion.
*/
WALK_AF_CAPS(caps, ac)
@ -411,7 +411,7 @@ bgp_write_capabilities(struct bgp_conn *conn, byte *buf)
return buf;
}
static void
static int
bgp_read_capabilities(struct bgp_conn *conn, struct bgp_caps *caps, byte *pos, int len)
{
struct bgp_proto *p = conn->bgp;
@ -577,11 +577,11 @@ bgp_read_capabilities(struct bgp_conn *conn, struct bgp_caps *caps, byte *pos, i
}
}
return;
return 0;
err:
bgp_error(conn, 2, 0, NULL, 0);
return;
return -1;
}
static int
@ -621,36 +621,62 @@ bgp_check_capabilities(struct bgp_conn *conn)
}
static int
bgp_read_options(struct bgp_conn *conn, byte *pos, int len)
bgp_read_options(struct bgp_conn *conn, byte *pos, uint len, uint rest)
{
struct bgp_proto *p = conn->bgp;
struct bgp_caps *caps;
int ol;
int ext = 0;
/* Handle extended length (draft-ietf-idr-ext-opt-param-07) */
if ((len > 0) && (rest > 0) && (pos[0] == 255))
{
if (rest < 3)
goto err;
/* Update pos/len to describe optional data */
len = get_u16(pos+1);
ext = 1;
pos += 3;
rest -= 3;
}
/* Verify that optional data fits into OPEN packet */
if (len > rest)
goto err;
/* Max number of announced AFIs is limited by max option length (255) */
caps = alloca(sizeof(struct bgp_caps) + 64 * sizeof(struct bgp_af_caps));
memset(caps, 0, sizeof(struct bgp_caps));
/* Length of option parameter header */
uint hlen = ext ? 3 : 2;
while (len > 0)
{
if ((len < 2) || (len < (2 + pos[1])))
{ bgp_error(conn, 2, 0, NULL, 0); return -1; }
if (len < hlen)
goto err;
ol = pos[1];
if (pos[0] == 2)
uint otype = get_u8(pos);
uint olen = ext ? get_u16(pos+1) : get_u8(pos+1);
if (len < (hlen + olen))
goto err;
if (otype == 2)
{
/* BGP capabilities, RFC 5492 */
if (p->cf->capabilities)
bgp_read_capabilities(conn, caps, pos + 2, ol);
if (bgp_read_capabilities(conn, caps, pos + hlen, olen) < 0)
return -1;
}
else
{
/* Unknown option */
bgp_error(conn, 2, 4, pos, ol); /* FIXME: ol or ol+2 ? */
bgp_error(conn, 2, 4, pos, hlen + olen);
return -1;
}
ADVANCE(pos, len, 2 + ol);
ADVANCE(pos, len, hlen + olen);
}
uint n = sizeof(struct bgp_caps) + caps->af_count * sizeof(struct bgp_af_caps);
@ -658,6 +684,10 @@ bgp_read_options(struct bgp_conn *conn, byte *pos, int len)
memcpy(conn->remote_caps, caps, n);
return 0;
err:
bgp_error(conn, 2, 0, NULL, 0);
return -1;
}
static byte *
@ -676,12 +706,29 @@ bgp_create_open(struct bgp_conn *conn, byte *buf)
if (p->cf->capabilities)
{
/* Prepare local_caps and write capabilities to buffer */
byte *end = bgp_write_capabilities(conn, buf+12);
uint len = end - (buf+12);
byte *pos = buf+12;
byte *end = bgp_write_capabilities(conn, pos);
uint len = end - pos;
buf[9] = len + 2; /* Optional parameters length */
buf[10] = 2; /* Option 2: Capability list */
buf[11] = len; /* Option data length */
if (len < 254)
{
buf[9] = len + 2; /* Optional parameters length */
buf[10] = 2; /* Option 2: Capability list */
buf[11] = len; /* Option data length */
}
else /* draft-ietf-idr-ext-opt-param-07 */
{
/* Move capabilities 4 B forward */
memmove(buf + 16, pos, len);
pos = buf + 16;
end = pos + len;
buf[9] = 255; /* Non-ext OP length, fake */
buf[10] = 255; /* Non-ext OP type, signals extended length */
put_u16(buf+11, len + 3); /* Extended optional parameters length */
buf[13] = 2; /* Option 2: Capability list */
put_u16(buf+14, len); /* Option extended data length */
}
return end;
}
@ -705,8 +752,8 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, uint len)
if (conn->state != BS_OPENSENT)
{ bgp_error(conn, 5, fsm_err_subcode[conn->state], NULL, 0); return; }
/* Check message contents */
if (len < 29 || len != 29 + (uint) pkt[28])
/* Check message length */
if (len < 29)
{ bgp_error(conn, 1, 2, pkt+16, 2); return; }
if (pkt[19] != BGP_VERSION)
@ -717,7 +764,7 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, uint len)
id = get_u32(pkt+24);
BGP_TRACE(D_PACKETS, "Got OPEN(as=%d,hold=%d,id=%R)", asn, hold, id);
if (bgp_read_options(conn, pkt+29, pkt[28]) < 0)
if (bgp_read_options(conn, pkt+29, pkt[28], len-29) < 0)
return;
if (hold > 0 && hold < 3)