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net: simplify non-cgo DNS exchange

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Also does less buffer allocation in case of TCP fallback.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/12925043
This commit is contained in:
Mikio Hara 2013-08-15 05:08:08 +09:00
parent 3a93626b49
commit 2eb7c6ec8a
1 changed files with 7 additions and 10 deletions
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17
src/pkg/net/dnsclient_unix.go
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@ -26,13 +26,7 @@ import (
// Send a request on the connection and hope for a reply.
// Up to cfg.attempts attempts.
func exchange(cfg *dnsConfig, c Conn, name string, qtype uint16) (*dnsMsg, error) {
var useTCP bool
switch c.(type) {
case *UDPConn:
useTCP = false
case *TCPConn:
useTCP = true
}
_, useTCP := c.(*TCPConn)
if len(name) >= 256 {
return nil, &DNSError{Err: "name too long", Name: name}
}
@ -69,8 +63,11 @@ func exchange(cfg *dnsConfig, c Conn, name string, qtype uint16) (*dnsMsg, error
continue
}
}
buf = make([]byte, uint16(buf[0])<<8+uint16(buf[1]))
n, err = io.ReadFull(c, buf)
mlen := int(buf[0])<<8 | int(buf[1])
if mlen > len(buf) {
buf = make([]byte, mlen)
}
n, err = io.ReadFull(c, buf[:mlen])
} else {
n, err = c.Read(buf)
}
@ -80,7 +77,7 @@ func exchange(cfg *dnsConfig, c Conn, name string, qtype uint16) (*dnsMsg, error
}
return nil, err
}
buf = buf[0:n]
buf = buf[:n]
in := new(dnsMsg)
if !in.Unpack(buf) || in.id != out.id {
continue