ref: ba1476058afaffc3f24ca8fbde11234def04d1bf
dir: /lib/std/resolve+posixy.myr/
use sys
use "alloc"
use "chartype"
use "die"
use "endian"
use "extremum"
use "hashfuncs"
use "htab"
use "ipparse"
use "now"
use "option"
use "result"
use "slcp"
use "sldup"
use "sleq"
use "slpush"
use "slurp"
use "strfind"
use "strsplit"
use "strstrip"
use "threadhooks"
use "types"
use "utf"
pkg std =
type rectype = union
`DnsA /* host address */
`DnsNS /* authoritative name server */
`DnsCNAME /* canonical name for an alias */
`DnsSOA /* marks the start of a zone of authority */
`DnsWKS /* well known service description */
`DnsPTR /* domain name pointer */
`DnsHINFO /* host information */
`DnsMINFO /* mailbox or mail list information */
`DnsMX /* mail exchange */
`DnsTXT /* text strings */
`DnsAAAA /* ipv6 host address */
`DnsInval /* invalid */
;;
type resolveerr = union
`Timeout
`Badconn
`Badhost
`Badsrv
`Badquery
`Badresp
;;
type hostinfo = struct
fam : sys.sockfam
stype : sys.socktype
ttl : uint32
addr : netaddr
stale : time
rtype : rectype
;;
const resolve : (host : byte[:] -> result(hostinfo[:], resolveerr))
const resolvemx : (host : byte[:] -> result(hostinfo[:], resolveerr))
const resolverec : (host : byte[:], t : rectype[:] -> result(hostinfo[:], resolveerr))
;;
const Hostfile = "/etc/hosts"
const Resolvfile = "/etc/resolv.conf"
const Timeout = 2_000
const Maxns = 5
var initdone : bool = false
var hostmap : htab(byte[:], hostinfo)#
var dnscache : htab(byte[:], hostinfo)#
var search : byte[:][:]
var nameservers : netaddr[:]
const resolve = {host
/*TODO: v4 and v6 */
-> resolverec(host, [`DnsA, `DnsAAAA][:])
}
const resolvemx = {host
-> resolverec(host, [`DnsMX][:])
}
const resolverec = {host, tl
if !initdone /* avoid extra contention */
lock(netlck)
if !initdone
hostmap = mkht()
dnscache = mkht()
loadhosts()
loadresolv()
initdone = true
;;
unlock(netlck)
;;
for t : tl
match findhost(host, rectype(t))
| `Some hinf:
-> `Ok sldup([hinf][:])
| `None:
-> dnsresolve(host, rectype(t))
;;
;;
-> `Err `Badquery
}
const findhost = {host, t
var h
lock(netlck)
match htget(dnscache, host)
| `std.Some inf:
if rectype(inf.rtype) != t
h = `std.None
elif inf.stale > std.now()
h = `std.Some inf
else
h = htget(hostmap, host)
;;
| `std.None:
h = htget(hostmap, host)
;;
unlock(netlck)
-> h
}
const loadhosts = {
var h
var lines
match slurp(Hostfile)
| `Ok d: h = d
| `Err m: -> void
;;
lines = strsplit(h, "\n")
for l : lines
/* trim comment */
match strfind(l, "#")
| `Some idx: l = l[:idx]
| `None: /* whole line */
;;
match word(l)
| `Some (ip, rest):
match ipparse(ip)
| `Some addr:
addhosts(addr, ip, rest)
| `None:
/*
invalid addresses are ignored: we don't want to break stuff
with invalid or unsupported addresses
*/
;;
| `None:
;;
;;
slfree(lines)
slfree(h)
}
const addhosts = {addr, as, str
var hinf
var fam
match addr
| `Ipv4 _: fam = sys.Afinet
| `Ipv6 _: fam = sys.Afinet6
;;
while true
match word(str)
| `Some (name, rest):
str = rest
if hthas(hostmap, name)
continue
;;
hinf = [
.fam=fam,
.stype = 0,
.ttl = 0,
.addr = addr
]
htput(hostmap, sldup(name), hinf)
| `None:
-> void
;;
;;
}
const loadresolv = {
var h
var lines
match slurp(Resolvfile)
| `Ok d: h = d
| `Err m: -> void
;;
lines = strsplit(h, "\n")
for l : lines
match strfind(l, "#")
| `Some _idx: l = l[:_idx]
| `None:
;;
match word(l)
| `Some ("nameserver", srv):
addns(srv)
| `Some (_, rest):
/* invalid or unrecognized commands */
| `None:
/* unrecognized lines */
;;
;;
slfree(lines)
slfree(h)
}
const addns = {rest
match word(rest)
| `Some (name, _):
match ipparse(name)
| `Some addr:
slpush(&nameservers, addr)
| `None:
/* nothing */
;;
| `None:
/* nothing */
;;
}
const word = {s
var c, len
len = 0
s = strfstrip(s)
for c = decode(s[len:]); c != Badchar && !isblank(c); c = decode(s[len:])
len += charlen(c)
;;
if len == 0
-> `None
else
-> `Some (s[:len], s[len:])
;;
}
const dnsresolve = {host, rt
var srv : sys.pollfd[Maxns]
var ret, fd, cutoff
if !valid(host)
-> `Err (`Badhost)
;;
cutoff = std.min(Maxns, nameservers.len)
for var i = 0; i < cutoff; i++
fd=dnsconnect(nameservers[i])
if fd != -1
srv[i] = [
.fd=fd,
.events=sys.Pollout,
.revents=0,
]
;;
;;
ret = dnsquery(srv[:cutoff], host, rt)
for s : srv[:cutoff]
sys.close(s.fd)
;;
-> ret
}
const dnsconnect = {ns
var sa4 : sys.sockaddr_in
var sa6 : sys.sockaddr_in6
var sa : sys.sockaddr#
var sock, sz
var status
match ns
| `Ipv4 bits:
sa4=[.fam=sys.Afinet, .addr=bits, .port=hosttonet(53)]
sa = (&sa4 : sys.sockaddr#)
sz = sizeof(sys.sockaddr_in)
| `Ipv6 bits:
sa6=[.fam=sys.Afinet6, .addr=bits, .port=hosttonet(53)]
sa = (&sa6 : sys.sockaddr#)
sz = sizeof(sys.sockaddr_in6)
;;
sock = sys.socket(sa.fam, sys.Sockdgram, 0)
if sock < 0
-> -1
;;
status = sys.connect(sock, sa, sz)
if status < 0
sys.close(sock)
-> -1
;;
-> sock
}
const dnsquery = {srv, host, t
var pkt : byte[512] /* big enough */
var id : uint16[Maxns]
var query
var fail
var giveup
fail = 0
giveup = now() + 1000*Timeout
while true
/* all failed */
if fail == srv.len
break
;;
var r = sys.poll(srv, (giveup - std.now() : int)/1000)
if r < 0
-> `Err `Badconn
elif r == 0
-> `Err `Timeout
;;
for var i = 0; i < srv.len; i++
var s = &srv[i]
if (s.revents & sys.Pollout) != 0
(id[i], query) = mkquery(host, t)
sys.write(s.fd, query)
s.events = sys.Pollin
elif (s.revents & sys.Pollin) != 0
var n = sys.read(s.fd, pkt[:])
if n < 0
-> `Err `Badconn
;;
var inf = hosts(pkt[:n], host, id[i])
match inf
| `std.Err `Badresp:
/* continue polling */
| _:
-> inf
;;
else
fail++
;;
;;
;;
-> `Err (`Badsrv)
}
const Qr : uint16 = 1 << 0
const Aa : uint16 = 1 << 5
const Tc : uint16 = 1 << 6
const Rd : uint16 = 1 << 7
const Ra : uint16 = 1 << 8
var nextid : uint16 = 42
const mkquery = {host, t
var pkt : byte[512] /* big enough */
var off : size
/* header */
off = 0
nextid++
off += pack16(pkt[:], off, nextid) /* id */
off += pack16(pkt[:], off, Ra) /* flags */
off += pack16(pkt[:], off, 1) /* qdcount */
off += pack16(pkt[:], off, 0) /* ancount */
off += pack16(pkt[:], off, 0) /* nscount */
off += pack16(pkt[:], off, 0) /* arcount */
/* query */
off += packname(pkt[:], off, host) /* host */
off += pack16(pkt[:], off, (t : uint16)) /* qtype: a record */
off += pack16(pkt[:], off, 0x1) /* qclass: inet4 */
-> (nextid, pkt[:off])
}
const hosts = {pkt, host, id
var off, ni
var r, n, q, a, t, ttl
var hinf : hostinfo[:]
var v6dat : byte[16]
off = 0
/* parse header */
(r, off) = unpack16(pkt, off) /* id */
if r != id
-> `Err `Badresp
;;
(_, off) = unpack16(pkt, off) /* flags */
(q, off) = unpack16(pkt, off) /* qdcount */
(a, off) = unpack16(pkt, off) /* ancount */
(_, off) = unpack16(pkt, off) /* nscount */
(_, off) = unpack16(pkt, off) /* arcount */
/* skip past query records */
for var i = 0; i < q; i++
off = skipname(pkt, off) /* name */
(_, off) = unpack16(pkt, off) /* type */
(_, off) = unpack16(pkt, off) /* class */
;;
/* parse answer records */
ni = 0
hinf = slalloc((a : size))
for var i = 0; i < a; i++
off = skipname(pkt, off) /* name */
(t, off) = unpack16(pkt, off) /* type */
(_, off) = unpack16(pkt, off) /* class */
(ttl, off) = unpack32(pkt, off) /* ttl */
(n, off) = unpack16(pkt, off) /* rdatalen */
hinf[ni].ttl = ttl
hinf[ni].stale = (ttl * 1_000_000 : time) + std.now()
hinf[ni].rtype = id2type(t)
match hinf[ni].rtype
| `DnsA:
/* the thing we're interested in: our IP address */
hinf[ni].addr = `Ipv4 [pkt[off], pkt[off+1], pkt[off+2], pkt[off+3]]
off += 4;
ni++
| `DnsAAAA:
std.slcp(v6dat[:], pkt[off:off+16])
hinf[ni].addr = `Ipv6 v6dat
off += 16
ni++
| _:
off += (n : std.size)
;;
;;
lock(netlck)
if ni != 0 && hinf[0].ttl != 0
std.htput(dnscache, std.sldup(host), hinf[0])
;;
unlock(netlck)
-> `Ok hinf[:ni]
}
const skipname = {pkt, off
var sz
for sz = (pkt[off] : size); sz != 0; sz = (pkt[off] : size)
/* ptr is 2 bytes */
if sz & 0xC0 == 0xC0
-> off + 2
else
off += sz + 1
;;
;;
-> off + 1
}
const pack16 = {buf, off, v
buf[off] = ((v & 0xff00) >> 8 : byte)
buf[off+1] = ((v & 0x00ff) >> 0 : byte)
-> sizeof(uint16) /* we always write one uint16 */
}
const unpack16 = {buf, off
var v
v = 0
v |= (buf[off + 0] : uint16) << 8
v |= (buf[off + 1] : uint16) << 0
-> (v, off+sizeof(uint16))
}
const unpack32 = {buf, off
var v
v = (buf[off] : uint32) << 24
v |= (buf[off+1] : uint32) << 32
v |= (buf[off+2] : uint32) << 8
v |= (buf[off+3] : uint32)
-> (v, off+sizeof(uint32))
}
const packname = {buf, off : size, host
var start
var last
start = off
last = 0
for var i = 0; i < host.len; i++
if host[i] == ('.' : byte)
off += addseg(buf, off, host[last:i])
last = i + 1
;;
;;
if host[host.len - 1] != ('.' : byte)
off += addseg(buf, off, host[last:])
;;
off += addseg(buf, off, "") /* null terminating segment */
-> off - start
}
const addseg = {buf, off, str
buf[off] = (str.len : byte)
slcp(buf[off + 1 : off + str.len + 1], str)
-> str.len + 1
}
const valid = {host : byte[:]
var i
var seglen
/* maximum length: 255 chars */
if host.len > 255
-> false
;;
seglen = 0
for i = 0; i < host.len; i++
if host[i] == ('.' : byte)
seglen = 0
;;
if seglen > 63
-> false
;;
if host[i] & 0x80 != 0
-> false
;;
;;
-> true
}
const id2type = {rtype
match rtype
| 1: -> `DnsA
| 2: -> `DnsNS
| 5: -> `DnsCNAME
| 6: -> `DnsSOA
| 11: -> `DnsWKS
| 12: -> `DnsPTR
| 13: -> `DnsHINFO
| 14: -> `DnsMINFO
| 15: -> `DnsMX
| 16: -> `DnsTXT
| 28: -> `DnsAAAA
| _: -> `DnsInval
;;
}
const rectype = {rtype
match rtype
| `DnsA: -> 1 /* host address */
| `DnsNS: -> 2 /* authoritative name server */
| `DnsCNAME: -> 5 /* canonical name for an alias */
| `DnsSOA: -> 6 /* marks the start of a zone of authority */
| `DnsWKS: -> 11 /* well known service description */
| `DnsPTR: -> 12 /* domain name pointer */
| `DnsHINFO: -> 13 /* host information */
| `DnsMINFO: -> 14 /* mailbox or mail list information */
| `DnsMX: -> 15 /* mail exchange */
| `DnsTXT: -> 16 /* text strings */
| `DnsAAAA: -> 28 /* ipv6 host address */
| `DnsInval: -> -1
;;
}