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dns: add some comments

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This commit is contained in:
nadoo 2018-08-06 00:46:07 +08:00
parent 09b6d59394
commit 5467e4bbc1
1 changed files with 6 additions and 10 deletions
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16
dns/client.go
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@ -116,12 +116,13 @@ func (c *Client) exchange(qname string, reqBytes []byte, preferTCP bool) (server
servers := c.GetServers(qname)
for _, server = range servers {
rc, err := dialer.Dial(network, server)
// TODO: check the timeout setting here, some dns client has 5 seconds timeout
// TODO: support timeout setting for different upstream server
rc.SetDeadline(time.Now().Add(time.Duration(3) * time.Second))
if err != nil {
log.F("[dns] failed to connect to server %v: %v", server, err)
continue
}
defer rc.Close()
switch network {
case "tcp":
@ -141,8 +142,6 @@ func (c *Client) exchange(qname string, reqBytes []byte, preferTCP bool) (server
// exchangeTCP exchange with server over tcp
func (c *Client) exchangeTCP(rc net.Conn, reqBytes []byte) ([]byte, error) {
defer rc.Close()
if _, err := rc.Write(reqBytes); err != nil {
log.F("[dns] failed to write req message: %v", err)
return nil, err
@ -168,8 +167,6 @@ func (c *Client) exchangeTCP(rc net.Conn, reqBytes []byte) ([]byte, error) {
// exchangeUDP exchange with server over udp
func (c *Client) exchangeUDP(rc net.Conn, reqBytes []byte) ([]byte, error) {
defer rc.Close()
if _, err := rc.Write(reqBytes[2:]); err != nil {
log.F("[dns] failed to write req message: %v", err)
return nil, err
@ -185,12 +182,12 @@ func (c *Client) exchangeUDP(rc net.Conn, reqBytes []byte) ([]byte, error) {
return reqBytes[:2+n], nil
}
// SetServer .
// SetServer sets a upstream dns server for the given domain
func (c *Client) SetServer(domain string, servers ...string) {
c.upServerMap[domain] = append(c.upServerMap[domain], servers...)
}
// GetServers .
// GetServers gets upstream dns servers for the given domain
func (c *Client) GetServers(domain string) []string {
domainParts := strings.Split(domain, ".")
length := len(domainParts)
@ -202,11 +199,10 @@ func (c *Client) GetServers(domain string) []string {
}
}
// TODO:
return c.upServers
}
// AddHandler .
// AddHandler adds a custom handler to handle the resolved result (A and AAAA)
func (c *Client) AddHandler(h HandleFunc) {
c.handlers = append(c.handlers, h)
}
@ -232,7 +228,7 @@ func (c *Client) AddRecord(record string) error {
return nil
}
// GenResponse .
// GenResponse generates a dns response message for the given domani an ip address
func (c *Client) GenResponse(domain string, ip string) (*Message, error) {
ipb := net.ParseIP(ip)
if ipb == nil {