libc/inet/resolv.c:

Collapse __length_dotted into __length_question (the sole user of it).
Make __length_question and __decode_answer static, they are used only once
  by only one function.
Delete __decode_question, it is unused.
All in all, four less .o files in libc.a.
Document what __dns_lookup returns (length of the packet).
Propagate packet len into __decode_answer, __length_question, __decode_dotted
  and check that we do not use data past the end of the packet.
Rename some variables/parameters to better names (len -> packet_len,
  data -> packet etc).
Add mini-doc how DNS packets look like.
Style cleanup.

libc/inet/Makefile.in

@@ -34,8 +34,8 @@ endif
 
 # multi source resolv.c
 resolv_CSRC += \
-	encodeh.c decodeh.c encoded.c decoded.c lengthd.c \
-	encodeq.c decodeq.c encodea.c decodea.c lengthq.c \
+	encodeh.c decodeh.c encoded.c decoded.c \
+	encodeq.c encodea.c \
 	dnslookup.c opennameservers.c closenameservers.c \
 	read_etc_hosts_r.c get_hosts_byaddr_r.c get_hosts_byname_r.c \
 	getnameinfo.c \