[PATCH 3/3] babel: Parse subtlvs and skip TLVs with a mandatory subtlv
Toke Høiland-Jørgensen
toke at toke.dk
Mon Jun 5 23:49:54 CEST 2017
RFC6126bis formally introduces subtlvs to the Babel protocol, including
mandatory subtlvs. This adds support for parsing subtlvs to the Babel protocol
and skips TLVs that contain mandatory subtlvs, as per the spec.
For details, see section 4.4 of
https://tools.ietf.org/html/draft-ietf-babel-rfc6126bis-02
Signed-off-by: Toke Høiland-Jørgensen <toke at toke.dk>
---
proto/babel/babel.h | 5 ++++
proto/babel/packets.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 79 insertions(+), 4 deletions(-)
diff --git a/proto/babel/babel.h b/proto/babel/babel.h
index 236c1a3b..b6332446 100644
--- a/proto/babel/babel.h
+++ b/proto/babel/babel.h
@@ -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,
diff --git a/proto/babel/packets.c b/proto/babel/packets.c
index da7d8a50..4c0d88df 100644
--- a/proto/babel/packets.c
+++ b/proto/babel/packets.c
@@ -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 {
@@ -370,14 +371,33 @@ 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;
@@ -454,6 +474,7 @@ babel_read_next_hop(struct babel_tlv *hdr, union babel_msg *m UNUSED,
return PARSE_ERROR;
state->next_hop_v4 = ipa_from_ip4(get_ip4(&tlv->addr));
+ state->current_tlv_endpos += sizeof(ip4_addr);
return PARSE_IGNORE;
case BABEL_AE_IP6:
@@ -461,6 +482,7 @@ babel_read_next_hop(struct babel_tlv *hdr, union babel_msg *m UNUSED,
return PARSE_ERROR;
state->next_hop_v6 = ipa_from_ip6(get_ip6(&tlv->addr));
+ state->current_tlv_endpos += sizeof(ip6_addr);
return PARSE_IGNORE;
case BABEL_AE_IP6_LL:
@@ -468,6 +490,7 @@ babel_read_next_hop(struct babel_tlv *hdr, union babel_msg *m UNUSED,
return PARSE_ERROR;
state->next_hop_v6 = ipa_from_ip6(get_ip6_ll(&tlv->addr));
+ state->current_tlv_endpos += 8;
return PARSE_IGNORE;
default:
@@ -626,6 +649,7 @@ 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;
}
@@ -745,6 +769,7 @@ 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:
@@ -755,6 +780,7 @@ 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:
@@ -831,6 +857,7 @@ 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:
@@ -841,6 +868,7 @@ 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:
@@ -886,10 +914,45 @@ babel_write_seqno_request(struct babel_tlv *hdr, union babel_msg *m,
}
static inline int
+babel_read_subtlvs(struct babel_tlv *hdr,
+ union babel_msg *msg UNUSED,
+ struct babel_parse_state *state)
+{
+ struct babel_tlv *subtlv;
+
+ for (subtlv = (void *) hdr + state->current_tlv_endpos;
+ subtlv < hdr + TLV_LENGTH(hdr);
+ subtlv = NEXT_TLV(subtlv))
+ {
+ /*
+ * 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 (subtlv->type)
+ {
+ case BABEL_SUBTLV_PAD1:
+ case BABEL_SUBTLV_PADN:
+ break;
+ default:
+ /* unknown mandatory subtlv; PARSE_IGNORE ignores the whole TLV */
+ if (subtlv->type > 128)
+ {
+ DBG("babel: Mandatory subtlv %d found; skipping TLV\n", subtlv->type);
+ return PARSE_IGNORE;
+ }
+ break;
+ }
+ }
+
+ return PARSE_SUCCESS;
+}
+
+static inline int
babel_read_tlv(struct babel_tlv *hdr,
union babel_msg *msg,
struct babel_parse_state *state)
{
+ int res;
if ((hdr->type <= BABEL_TLV_PADN) ||
(hdr->type >= BABEL_TLV_MAX) ||
!tlv_data[hdr->type].read_tlv)
@@ -898,8 +961,15 @@ 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);
+ 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
--
2.13.0
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