Babel: Refactor TLV parsing code for easier reuse
In preparation for adding authentication checks, refactor the TLV walking code so it can be reused for a separate pass of the packet for authentication checks.
This commit is contained in:
Toke Høiland-Jørgensen
Ondrej Zajicek (work)
parent
589f7d1e4f
commit
69d10132a6
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@ -120,8 +120,19 @@ struct babel_subtlv_source_prefix {
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#define BABEL_UF_DEF_PREFIX 0x80
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#define BABEL_UF_ROUTER_ID 0x40
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struct babel_parse_state;
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struct babel_write_state;
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struct babel_tlv_data {
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u8 min_length;
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int (*read_tlv)(struct babel_tlv *hdr, union babel_msg *m, struct babel_parse_state *state);
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uint (*write_tlv)(struct babel_tlv *hdr, union babel_msg *m, struct babel_write_state *state, uint max_len);
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void (*handle_tlv)(union babel_msg *m, struct babel_iface *ifa);
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};
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struct babel_parse_state {
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const struct babel_tlv_data* (*get_tlv_data)(u8 type);
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const struct babel_tlv_data* (*get_subtlv_data)(u8 type);
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struct babel_proto *proto;
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struct babel_iface *ifa;
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ip_addr saddr;
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@ -167,6 +178,37 @@ struct babel_write_state {
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#define NET_SIZE(n) BYTES(net_pxlen(n))
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/* Helper macros to loop over a series of TLVs.
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* @start pointer to first TLV (void * or struct babel_tlv *)
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* @end byte * pointer to TLV stream end
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* @tlv struct babel_tlv pointer used as iterator
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* @frame_err boolean (u8) that will be set to 1 if a frame error occurred
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* @saddr source addr for use in log output
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* @ifname ifname for use in log output
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*/
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#define WALK_TLVS(start, end, tlv, frame_err, saddr, ifname) \
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for (tlv = start; \
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(byte *)tlv < end; \
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tlv = NEXT_TLV(tlv)) \
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{ \
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byte *loop_pos; \
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/* Ugly special case */ \
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if (tlv->type == BABEL_TLV_PAD1) \
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continue; \
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\
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/* The end of the common TLV header */ \
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loop_pos = (byte *)tlv + sizeof(struct babel_tlv); \
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if ((loop_pos > end) || (loop_pos + tlv->length > end)) \
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{ \
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LOG_PKT("Bad TLV from %I via %s type %d pos %d - framing error", \
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saddr, ifname, tlv->type, (byte *)tlv - (byte *)start); \
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frame_err = 1; \
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break; \
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}
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#define WALK_TLVS_END }
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static inline uint
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bytes_equal(u8 *b1, u8 *b2, uint maxlen)
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{
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@ -255,13 +297,6 @@ static uint babel_write_route_request(struct babel_tlv *hdr, union babel_msg *ms
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static uint babel_write_seqno_request(struct babel_tlv *hdr, union babel_msg *msg, struct babel_write_state *state, uint max_len);
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static int babel_write_source_prefix(struct babel_tlv *hdr, net_addr *net, uint max_len);
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struct babel_tlv_data {
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u8 min_length;
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int (*read_tlv)(struct babel_tlv *hdr, union babel_msg *m, struct babel_parse_state *state);
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uint (*write_tlv)(struct babel_tlv *hdr, union babel_msg *m, struct babel_write_state *state, uint max_len);
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void (*handle_tlv)(union babel_msg *m, struct babel_iface *ifa);
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};
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static const struct babel_tlv_data tlv_data[BABEL_TLV_MAX] = {
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[BABEL_TLV_ACK_REQ] = {
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sizeof(struct babel_tlv_ack_req),
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@ -319,6 +354,30 @@ static const struct babel_tlv_data tlv_data[BABEL_TLV_MAX] = {
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},
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};
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static const struct babel_tlv_data *get_packet_tlv_data(u8 type)
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{
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return type < sizeof(tlv_data) / sizeof(*tlv_data) ? &tlv_data[type] : NULL;
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}
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static const struct babel_tlv_data source_prefix_tlv_data = {
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sizeof(struct babel_subtlv_source_prefix),
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babel_read_source_prefix,
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NULL,
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NULL
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};
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static const struct babel_tlv_data *get_packet_subtlv_data(u8 type)
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{
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switch(type)
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{
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case BABEL_SUBTLV_SOURCE_PREFIX:
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return &source_prefix_tlv_data;
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default:
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return NULL;
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}
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}
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static int
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babel_read_ack_req(struct babel_tlv *hdr, union babel_msg *m,
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struct babel_parse_state *state)
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@ -1083,69 +1142,65 @@ babel_write_source_prefix(struct babel_tlv *hdr, net_addr *n, uint max_len)
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return len;
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}
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static inline int
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babel_read_subtlvs(struct babel_tlv *hdr,
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union babel_msg *msg,
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struct babel_parse_state *state)
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{
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const struct babel_tlv_data *tlv_data;
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struct babel_proto *p = state->proto;
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struct babel_tlv *tlv;
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byte *pos, *end = (byte *) hdr + TLV_LENGTH(hdr);
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byte *end = (byte *) hdr + TLV_LENGTH(hdr);
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u8 frame_err = 0;
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int res;
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for (tlv = (void *) hdr + state->current_tlv_endpos;
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(byte *) tlv < end;
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tlv = NEXT_TLV(tlv))
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WALK_TLVS((void *)hdr + state->current_tlv_endpos, end, tlv, frame_err,
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state->saddr, state->ifa->ifname)
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{
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/* Ugly special case */
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if (tlv->type == BABEL_TLV_PAD1)
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if (tlv->type == BABEL_SUBTLV_PADN)
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continue;
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/* The end of the common TLV header */
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pos = (byte *)tlv + sizeof(struct babel_tlv);
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if ((pos > end) || (pos + tlv->length > end))
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return PARSE_ERROR;
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/*
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* The subtlv type space is non-contiguous (due to the mandatory bit), so
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* use a switch for dispatch instead of the mapping array we use for TLVs
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*/
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switch (tlv->type)
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if (!state->get_subtlv_data ||
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!(tlv_data = state->get_subtlv_data(tlv->type)) ||
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!tlv_data->read_tlv)
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{
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case BABEL_SUBTLV_SOURCE_PREFIX:
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res = babel_read_source_prefix(tlv, msg, state);
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if (res != PARSE_SUCCESS)
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return res;
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break;
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case BABEL_SUBTLV_PADN:
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default:
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/* Unknown mandatory subtlv; PARSE_IGNORE ignores the whole TLV */
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if (tlv->type >= 128)
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return PARSE_IGNORE;
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break;
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return PARSE_IGNORE;
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continue;
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}
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}
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return PARSE_SUCCESS;
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res = tlv_data->read_tlv(tlv, msg, state);
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if (res != PARSE_SUCCESS)
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return res;
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}
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WALK_TLVS_END;
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return frame_err ? PARSE_ERROR : PARSE_SUCCESS;
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}
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static inline int
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static int
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babel_read_tlv(struct babel_tlv *hdr,
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union babel_msg *msg,
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struct babel_parse_state *state)
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{
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const struct babel_tlv_data *tlv_data;
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if ((hdr->type <= BABEL_TLV_PADN) ||
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(hdr->type >= BABEL_TLV_MAX) ||
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!tlv_data[hdr->type].read_tlv)
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(hdr->type >= BABEL_TLV_MAX))
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return PARSE_IGNORE;
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if (TLV_LENGTH(hdr) < tlv_data[hdr->type].min_length)
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tlv_data = state->get_tlv_data(hdr->type);
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if (!tlv_data || !tlv_data->read_tlv)
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return PARSE_IGNORE;
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if (TLV_LENGTH(hdr) < tlv_data->min_length)
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return PARSE_ERROR;
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state->current_tlv_endpos = tlv_data[hdr->type].min_length;
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state->current_tlv_endpos = tlv_data->min_length;
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int res = tlv_data[hdr->type].read_tlv(hdr, msg, state);
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int res = tlv_data->read_tlv(hdr, msg, state);
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if (res != PARSE_SUCCESS)
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return res;
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@ -1330,6 +1385,7 @@ static void
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babel_process_packet(struct babel_pkt_header *pkt, int len,
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ip_addr saddr, struct babel_iface *ifa)
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{
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u8 frame_err UNUSED = 0;
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struct babel_proto *p = ifa->proto;
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struct babel_tlv *tlv;
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struct babel_msg_node *msg;
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@ -1337,15 +1393,16 @@ babel_process_packet(struct babel_pkt_header *pkt, int len,
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int res;
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int plen = sizeof(struct babel_pkt_header) + get_u16(&pkt->length);
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byte *pos;
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byte *end = (byte *)pkt + plen;
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struct babel_parse_state state = {
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.proto = p,
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.ifa = ifa,
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.saddr = saddr,
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.next_hop_ip6 = saddr,
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.sadr_enabled = babel_sadr_enabled(p),
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.get_tlv_data = &get_packet_tlv_data,
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.get_subtlv_data = &get_packet_subtlv_data,
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.proto = p,
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.ifa = ifa,
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.saddr = saddr,
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.next_hop_ip6 = saddr,
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.sadr_enabled = babel_sadr_enabled(p),
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};
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if ((pkt->magic != BABEL_MAGIC) || (pkt->version != BABEL_VERSION))
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@ -1369,23 +1426,8 @@ babel_process_packet(struct babel_pkt_header *pkt, int len,
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/* First pass through the packet TLV by TLV, parsing each into internal data
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structures. */
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for (tlv = FIRST_TLV(pkt);
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(byte *)tlv < end;
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tlv = NEXT_TLV(tlv))
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WALK_TLVS(FIRST_TLV(pkt), end, tlv, frame_err, saddr, ifa->iface->name)
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{
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/* Ugly special case */
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if (tlv->type == BABEL_TLV_PAD1)
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continue;
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/* The end of the common TLV header */
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pos = (byte *)tlv + sizeof(struct babel_tlv);
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if ((pos > end) || (pos + tlv->length > end))
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{
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LOG_PKT("Bad TLV from %I via %s type %d pos %d - framing error",
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saddr, ifa->iface->name, tlv->type, (byte *)tlv - (byte *)pkt);
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break;
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}
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msg = sl_allocz(p->msg_slab);
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res = babel_read_tlv(tlv, &msg->msg, &state);
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if (res == PARSE_SUCCESS)
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@ -1405,8 +1447,9 @@ babel_process_packet(struct babel_pkt_header *pkt, int len,
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break;
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}
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}
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WALK_TLVS_END;
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/* Parsing done, handle all parsed TLVs */
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/* Parsing done, handle all parsed TLVs, regardless of any errors */
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WALK_LIST_FIRST(msg, msgs)
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{
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if (tlv_data[msg->msg.type].handle_tlv)
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