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Babel: Parse sub-TLVs and skip TLVs with mandatory sub-TLV

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RFC6126bis formally introduces sub-TLVs to the Babel protocol, including
mandatory sub-TLVs. This adds support for parsing sub-TLVs to the Babel
protocol and skips TLVs that contain mandatory sub-TLVs, as per the spec.

For details, see section 4.4 of
https://tools.ietf.org/html/draft-ietf-babel-rfc6126bis-02

Thanks to Toke Høiland-Jørgensen <toke@toke.dk> for the patch.
This commit is contained in:
Ondrej Zajicek (work) 2017-06-09 14:33:06 +02:00
parent b3c6273efa
commit 145ebfa1df
2 changed files with 79 additions and 4 deletions
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5
proto/babel/babel.h
View file

@ -78,6 +78,11 @@ enum babel_tlv_type {
BABEL_TLV_MAX
};
enum babel_subtlv_type {
BABEL_SUBTLV_PAD1 = 0,
BABEL_SUBTLV_PADN = 1
};
enum babel_iface_type {
/* In practice, UNDEF and WIRED give equivalent behaviour */
BABEL_IFACE_TYPE_UNDEF = 0,

78
proto/babel/packets.c
View file

@ -120,6 +120,7 @@ struct babel_parse_state {
u8 router_id_seen; /* router_id field is valid */
u8 def_ip6_prefix_seen; /* def_ip6_prefix is valid */
u8 def_ip4_prefix_seen; /* def_ip4_prefix is valid */
u8 current_tlv_endpos; /* End of self-terminating TLVs (offset from start) */
};
enum parse_result {
@ -379,14 +380,33 @@ babel_read_ihu(struct babel_tlv *hdr, union babel_msg *m,
if (msg->ae >= BABEL_AE_MAX)
return PARSE_IGNORE;
// We handle link-local IPs. In every other case, the addr field will be 0 but
// validation will succeed. The handler takes care of these cases.
if (msg->ae == BABEL_AE_IP6_LL)
/*
* We only actually read link-local IPs. In every other case, the addr field
* will be 0 but validation will succeed. The handler takes care of these
* cases. We handle them here anyway because we need the length for parsing
* subtlvs.
*/
switch (msg->ae)
{
case BABEL_AE_IP4:
if (TLV_OPT_LENGTH(tlv) < 4)
return PARSE_ERROR;
state->current_tlv_endpos += 4;
break;
case BABEL_AE_IP6:
if (TLV_OPT_LENGTH(tlv) < 16)
return PARSE_ERROR;
state->current_tlv_endpos += 16;
break;
case BABEL_AE_IP6_LL:
if (TLV_OPT_LENGTH(tlv) < 8)
return PARSE_ERROR;
msg->addr = ipa_from_ip6(get_ip6_ll(&tlv->addr));
state->current_tlv_endpos += 8;
break;
}
return PARSE_SUCCESS;
@ -463,6 +483,7 @@ babel_read_next_hop(struct babel_tlv *hdr, union babel_msg *m UNUSED,
return PARSE_ERROR;
state->next_hop_ip4 = ipa_from_ip4(get_ip4(&tlv->addr));
state->current_tlv_endpos += sizeof(ip4_addr);
return PARSE_IGNORE;
case BABEL_AE_IP6:
@ -470,6 +491,7 @@ babel_read_next_hop(struct babel_tlv *hdr, union babel_msg *m UNUSED,
return PARSE_ERROR;
state->next_hop_ip6 = ipa_from_ip6(get_ip6(&tlv->addr));
state->current_tlv_endpos += sizeof(ip6_addr);
return PARSE_IGNORE;
case BABEL_AE_IP6_LL:
@ -477,6 +499,7 @@ babel_read_next_hop(struct babel_tlv *hdr, union babel_msg *m UNUSED,
return PARSE_ERROR;
state->next_hop_ip6 = ipa_from_ip6(get_ip6_ll(&tlv->addr));
state->current_tlv_endpos += 8;
return PARSE_IGNORE;
default:
@ -639,6 +662,7 @@ babel_read_update(struct babel_tlv *hdr, union babel_msg *m,
msg->router_id = state->router_id;
msg->sender = state->saddr;
state->current_tlv_endpos += len;
return PARSE_SUCCESS;
}
@ -765,6 +789,7 @@ babel_read_route_request(struct babel_tlv *hdr, union babel_msg *m,
return PARSE_ERROR;
read_ip4_px(&msg->net, tlv->addr, tlv->plen);
state->current_tlv_endpos += BYTES(tlv->plen);
return PARSE_SUCCESS;
case BABEL_AE_IP6:
@ -775,6 +800,7 @@ babel_read_route_request(struct babel_tlv *hdr, union babel_msg *m,
return PARSE_ERROR;
read_ip6_px(&msg->net, tlv->addr, tlv->plen);
state->current_tlv_endpos += BYTES(tlv->plen);
return PARSE_SUCCESS;
case BABEL_AE_IP6_LL:
@ -851,6 +877,7 @@ babel_read_seqno_request(struct babel_tlv *hdr, union babel_msg *m,
return PARSE_ERROR;
read_ip4_px(&msg->net, tlv->addr, tlv->plen);
state->current_tlv_endpos += BYTES(tlv->plen);
return PARSE_SUCCESS;
case BABEL_AE_IP6:
@ -861,6 +888,7 @@ babel_read_seqno_request(struct babel_tlv *hdr, union babel_msg *m,
return PARSE_ERROR;
read_ip6_px(&msg->net, tlv->addr, tlv->plen);
state->current_tlv_endpos += BYTES(tlv->plen);
return PARSE_SUCCESS;
case BABEL_AE_IP6_LL:
@ -907,6 +935,42 @@ babel_write_seqno_request(struct babel_tlv *hdr, union babel_msg *m,
return len;
}
static inline int
babel_read_subtlvs(struct babel_tlv *hdr,
union babel_msg *msg UNUSED,
struct babel_parse_state *state)
{
struct babel_tlv *tlv;
for (tlv = (void *) hdr + state->current_tlv_endpos;
tlv < hdr + TLV_LENGTH(hdr);
tlv = NEXT_TLV(tlv))
{
/*
* The subtlv type space is non-contiguous (due to the mandatory bit), so
* use a switch for dispatch instead of the mapping array we use for TLVs
*/
switch (tlv->type)
{
case BABEL_SUBTLV_PAD1:
case BABEL_SUBTLV_PADN:
/* FIXME: Framing errors in PADN are silently ignored, see babel_process_packet() */
break;
default:
/* Unknown mandatory subtlv; PARSE_IGNORE ignores the whole TLV */
if (tlv->type > 128)
{
DBG("Babel: Mandatory subtlv %d found; skipping TLV\n", tlv->type);
return PARSE_IGNORE;
}
break;
}
}
return PARSE_SUCCESS;
}
static inline int
babel_read_tlv(struct babel_tlv *hdr,
union babel_msg *msg,
@ -920,8 +984,14 @@ babel_read_tlv(struct babel_tlv *hdr,
if (TLV_LENGTH(hdr) < tlv_data[hdr->type].min_length)
return PARSE_ERROR;
state->current_tlv_endpos = tlv_data[hdr->type].min_length;
memset(msg, 0, sizeof(*msg));
return tlv_data[hdr->type].read_tlv(hdr, msg, state);
int res = tlv_data[hdr->type].read_tlv(hdr, msg, state);
if (res != PARSE_SUCCESS)
return res;
return babel_read_subtlvs(hdr, msg, state);
}
static uint