}
}
if (!done) {
- uint32_t source,dest;
- /* Manufacture and send NAK packet */
- source=get_uint32(st->rbuf->start); /* Us */
- dest=get_uint32(st->rbuf->start+4); /* Them */
- Message(M_INFO,"udp (port %d): sending NAK\n",st->port);
- buffer_init(st->rbuf,0);
- buf_append_uint32(st->rbuf,dest);
- buf_append_uint32(st->rbuf,source);
- buf_append_uint32(st->rbuf,LABEL_NAK);
- sendto(st->fd, st->rbuf->start, st->rbuf->size, 0,
- (struct sockaddr *)&from, sizeof(from));
+ uint32_t msgtype;
+ if (st->rbuf->size>12 /* prevents traffic amplification */
+ && ((msgtype=get_uint32(st->rbuf->start+8))
+ != LABEL_NAK)) {
+ uint32_t source,dest;
+ /* Manufacture and send NAK packet */
+ source=get_uint32(st->rbuf->start); /* Us */
+ dest=get_uint32(st->rbuf->start+4); /* Them */
+ Message(M_INFO,"udp (port %d, peer %s):"
+ " %08"PRIx32"<-%08"PRIx32": %08"PRIx32":"
+ " unwanted/incorrect, sending NAK\n",
+ st->port, saddr_to_string(&from),
+ dest, source, msgtype);
+ buffer_init(st->rbuf,0);
+ buf_append_uint32(st->rbuf,dest);
+ buf_append_uint32(st->rbuf,source);
+ buf_append_uint32(st->rbuf,LABEL_NAK);
+ sendto(st->fd, st->rbuf->start, st->rbuf->size, 0,
+ (struct sockaddr *)&from, sizeof(from));
+ }
BUF_FREE(st->rbuf);
}
BUF_ASSERT_FREE(st->rbuf);