lib/promscrape: code prettifying for 8dd03ecf19

docs/CHANGELOG.md

@@ -2,6 +2,7 @@
 
 # tip
 
+* FEATURE: vmagent: add support for `proxy_url` config option in Prometheus scrape configs. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/503
 * FEATURE: remove parts with stale data as soon as they go outside the configured `-retentionPeriod`. Previously such parts may remain active for long periods of time. This should help reducing disk usage for `-retentionPeriod` smaller than one month.
 * FEATURE: vmalert: allow setting multiple values for `-notifier.tlsInsecureSkipVerify` command-line flag per each `-notifier.url`.
 

lib/netutil/proxy.go

@@ -1,124 +0,0 @@
-package netutil
-
-import (
-	"bufio"
-	"encoding/base64"
-	"fmt"
-	"net"
-	"net/url"
-	"strings"
-
-	"github.com/VictoriaMetrics/fasthttp"
-)
-
-// ProxyURL implements marshal interfaces for url.URL.
-type ProxyURL struct {
-	url *url.URL
-}
-
-// URL returns *url.URL.
-func (pu ProxyURL) URL() *url.URL {
-	return pu.url
-}
-
-// String implements String interface.
-func (pu ProxyURL) String() string {
-	if pu.url == nil {
-		return ""
-	}
-	return pu.url.String()
-}
-
-// MarshalYAML implements yaml.Marshaler interface.
-func (pu ProxyURL) MarshalYAML() (interface{}, error) {
-	if pu.url == nil {
-		return nil, nil
-	}
-	return pu.url.String(), nil
-}
-
-// UnmarshalYAML implements yaml.Unmarshaler interface.
-func (pu *ProxyURL) UnmarshalYAML(unmarshal func(interface{}) error) error {
-	var s string
-	if err := unmarshal(&s); err != nil {
-		return err
-	}
-	parsedURL, err := url.Parse(s)
-	if err != nil {
-		return fmt.Errorf("failed parse proxy_url=%q as *url.URL, err=%w", s, err)
-	}
-	pu.url = parsedURL
-	return nil
-}
-
-// GetProxyDialFunc returns dial proxy func for the given proxy url.
-// currently only http based proxy is supported.
-func GetProxyDialFunc(proxyURL *url.URL) (fasthttp.DialFunc, error) {
-	if strings.HasPrefix(proxyURL.Scheme, "http") {
-		return httpProxy(proxyURL.Host, MakeBasicAuthHeader(nil, proxyURL)), nil
-	}
-	return nil, fmt.Errorf("unknown scheme=%q for proxy_url: %q, must be http or https", proxyURL.Scheme, proxyURL)
-}
-
-func httpProxy(proxyAddr string, auth []byte) fasthttp.DialFunc {
-	return func(addr string) (net.Conn, error) {
-		var (
-			conn net.Conn
-			err  error
-		)
-		if TCP6Enabled() {
-			conn, err = fasthttp.DialDualStack(proxyAddr)
-		} else {
-			conn, err = fasthttp.Dial(proxyAddr)
-		}
-		if err != nil {
-			return nil, fmt.Errorf("cannot connect to the proxy=%q,err=%w", proxyAddr, err)
-		}
-		if err := MakeProxyConnectCall(conn, []byte(addr), auth); err != nil {
-			_ = conn.Close()
-			return nil, err
-		}
-		return conn, nil
-	}
-}
-
-// MakeBasicAuthHeader encodes and writes basic auth http header from url into given dst and returns it.
-func MakeBasicAuthHeader(dst []byte, url *url.URL) []byte {
-	if url == nil || url.User == nil {
-		return dst
-	}
-	if len(url.User.Username()) > 0 {
-		dst = append(dst, "Proxy-Authorization: Basic "...)
-		dst = append(dst, base64.StdEncoding.EncodeToString([]byte(url.User.String()))...)
-	}
-	return dst
-}
-
-// MakeProxyConnectCall execute CONNECT method to proxy with given destination address.
-func MakeProxyConnectCall(conn net.Conn, dstAddr, auth []byte) error {
-	conReq := make([]byte, 0, 10)
-	conReq = append(conReq, []byte("CONNECT ")...)
-	conReq = append(conReq, dstAddr...)
-	conReq = append(conReq, []byte(" HTTP/1.1\r\n")...)
-	if len(auth) > 0 {
-		conReq = append(conReq, auth...)
-		conReq = append(conReq, []byte("\r\n")...)
-	}
-	conReq = append(conReq, []byte("\r\n")...)
-
-	res := fasthttp.AcquireResponse()
-	defer fasthttp.ReleaseResponse(res)
-	res.SkipBody = true
-	if _, err := conn.Write(conReq); err != nil {
-		return err
-	}
-	if err := res.Read(bufio.NewReader(conn)); err != nil {
-		_ = conn.Close()
-		return fmt.Errorf("cannot read CONNECT response from proxy, err=%w", err)
-	}
-	if res.Header.StatusCode() != 200 {
-		_ = conn.Close()
-		return fmt.Errorf("unexpected proxy response status code, want: 200, get: %d", res.Header.StatusCode())
-	}
-	return nil
-}

lib/promscrape/client.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"io/ioutil"
 	"net/http"
+	"net/url"
 	"strings"
 	"time"
 
@@ -66,10 +67,14 @@ func newClient(sw *ScrapeWork) *client {
 			host += ":443"
 		}
 	}
+	dialFunc, err := newStatDialFunc(sw.ProxyURL, tlsCfg)
+	if err != nil {
+		logger.Fatalf("cannot create dial func: %s", err)
+	}
 	hc := &fasthttp.HostClient{
 		Addr:                         host,
 		Name:                         "vm_promscrape",
-		Dial:                         getDialStatConn(sw.ProxyURL),
+		Dial:                         dialFunc,
 		IsTLS:                        isTLS,
 		TLSConfig:                    tlsCfg,
 		MaxIdleConnDuration:          2 * sw.ScrapeInterval,
@@ -80,10 +85,14 @@ func newClient(sw *ScrapeWork) *client {
 	}
 	var sc *http.Client
 	if *streamParse || sw.StreamParse {
+		var proxy func(*http.Request) (*url.URL, error)
+		if proxyURL := sw.ProxyURL.URL(); proxyURL != nil {
+			proxy = http.ProxyURL(proxyURL)
+		}
 		sc = &http.Client{
 			Transport: &http.Transport{
 				TLSClientConfig:     tlsCfg,
-				Proxy:               http.ProxyURL(sw.ProxyURL),
+				Proxy:               proxy,
 				TLSHandshakeTimeout: 10 * time.Second,
 				IdleConnTimeout:     2 * sw.ScrapeInterval,
 				DisableCompression:  *disableCompression || sw.DisableCompression,

lib/promscrape/config.go

@@ -12,7 +12,6 @@ import (
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/envtemplate"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promauth"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promrelabel"
@@ -24,6 +23,7 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promscrape/discovery/gce"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promscrape/discovery/kubernetes"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promscrape/discovery/openstack"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/proxy"
 	"gopkg.in/yaml.v2"
 )
 
@@ -72,7 +72,7 @@ type ScrapeConfig struct {
 	BasicAuth            *promauth.BasicAuthConfig   `yaml:"basic_auth,omitempty"`
 	BearerToken          string                      `yaml:"bearer_token,omitempty"`
 	BearerTokenFile      string                      `yaml:"bearer_token_file,omitempty"`
-	ProxyURL             netutil.ProxyURL            `yaml:"proxy_url,omitempty"`
+	ProxyURL             proxy.URL                   `yaml:"proxy_url,omitempty"`
 	TLSConfig            *promauth.TLSConfig         `yaml:"tls_config,omitempty"`
 	StaticConfigs        []StaticConfig              `yaml:"static_configs,omitempty"`
 	FileSDConfigs        []FileSDConfig              `yaml:"file_sd_configs,omitempty"`
@@ -497,7 +497,7 @@ func getScrapeWorkConfig(sc *ScrapeConfig, baseDir string, globalCfg *GlobalConf
 		metricsPath:          metricsPath,
 		scheme:               scheme,
 		params:               params,
-		proxyURL:             sc.ProxyURL.URL(),
+		proxyURL:             sc.ProxyURL,
 		authConfig:           ac,
 		honorLabels:          honorLabels,
 		honorTimestamps:      honorTimestamps,
@@ -519,7 +519,7 @@ type scrapeWorkConfig struct {
 	metricsPath          string
 	scheme               string
 	params               map[string][]string
-	proxyURL             *url.URL
+	proxyURL             proxy.URL
 	authConfig           *promauth.Config
 	honorLabels          bool
 	honorTimestamps      bool

lib/promscrape/discovery/consul/api.go

@@ -58,7 +58,7 @@ func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 		}
 		apiServer = scheme + "://" + apiServer
 	}
-	client, err := discoveryutils.NewClient(apiServer, ac, sdc.ProxyURL.URL())
+	client, err := discoveryutils.NewClient(apiServer, ac, sdc.ProxyURL)
 	if err != nil {
 		return nil, fmt.Errorf("cannot create HTTP client for %q: %w", apiServer, err)
 	}

lib/promscrape/discovery/consul/consul.go

@@ -3,8 +3,8 @@ package consul
 import (
 	"fmt"
 
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promauth"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/proxy"
 )
 
 // SDConfig represents service discovery config for Consul.
@@ -17,7 +17,7 @@ type SDConfig struct {
 	Scheme       string              `yaml:"scheme,omitempty"`
 	Username     string              `yaml:"username"`
 	Password     string              `yaml:"password"`
-	ProxyURL     netutil.ProxyURL    `yaml:"proxy_url,omitempty"`
+	ProxyURL     proxy.URL           `yaml:"proxy_url,omitempty"`
 	TLSConfig    *promauth.TLSConfig `yaml:"tls_config,omitempty"`
 	Services     []string            `yaml:"services,omitempty"`
 	Tags         []string            `yaml:"tags,omitempty"`

lib/promscrape/discovery/dockerswarm/api.go

@@ -39,7 +39,7 @@ func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 	if err != nil {
 		return nil, err
 	}
-	client, err := discoveryutils.NewClient(sdc.Host, ac, sdc.ProxyURL.URL())
+	client, err := discoveryutils.NewClient(sdc.Host, ac, sdc.ProxyURL)
 	if err != nil {
 		return nil, fmt.Errorf("cannot create HTTP client for %q: %w", sdc.Host, err)
 	}

lib/promscrape/discovery/dockerswarm/dockerswarm.go

@@ -3,8 +3,8 @@ package dockerswarm
 import (
 	"fmt"
 
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promauth"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/proxy"
 )
 
 // SDConfig represents docker swarm service discovery configuration
@@ -16,7 +16,7 @@ type SDConfig struct {
 	Port    int      `yaml:"port,omitempty"`
 	Filters []Filter `yaml:"filters,omitempty"`
 
-	ProxyURL  netutil.ProxyURL    `yaml:"proxy_url,omitempty"`
+	ProxyURL  proxy.URL           `yaml:"proxy_url,omitempty"`
 	TLSConfig *promauth.TLSConfig `yaml:"tls_config,omitempty"`
 	// refresh_interval is obtained from `-promscrape.dockerswarmSDCheckInterval` command-line option
 	BasicAuth       *promauth.BasicAuthConfig `yaml:"basic_auth,omitempty"`

lib/promscrape/discovery/eureka/api.go

@@ -43,7 +43,7 @@ func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 		}
 		apiServer = scheme + "://" + apiServer
 	}
-	client, err := discoveryutils.NewClient(apiServer, ac, sdc.ProxyURL.URL())
+	client, err := discoveryutils.NewClient(apiServer, ac, sdc.ProxyURL)
 	if err != nil {
 		return nil, fmt.Errorf("cannot create HTTP client for %q: %w", apiServer, err)
 	}

lib/promscrape/discovery/eureka/eureka.go

@@ -5,9 +5,9 @@ import (
 	"fmt"
 	"strconv"
 
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promauth"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promscrape/discoveryutils"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/proxy"
 )
 
 const appsAPIPath = "/apps"
@@ -22,7 +22,7 @@ type SDConfig struct {
 	Scheme     string              `yaml:"scheme,omitempty"`
 	Username   string              `yaml:"username"`
 	Password   string              `yaml:"password"`
-	ProxyURL   netutil.ProxyURL    `yaml:"proxy_url,omitempty"`
+	ProxyURL   proxy.URL           `yaml:"proxy_url,omitempty"`
 	TLSConfig  *promauth.TLSConfig `yaml:"tls_config,omitempty"`
 	// RefreshInterval time.Duration `yaml:"refresh_interval"`
 	// refresh_interval is obtained from `-promscrape.ec2SDCheckInterval` command-line option.

lib/promscrape/discovery/kubernetes/api.go

@@ -56,7 +56,7 @@ func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 		}
 		ac = acNew
 	}
-	client, err := discoveryutils.NewClient(apiServer, ac, sdc.ProxyURL.URL())
+	client, err := discoveryutils.NewClient(apiServer, ac, sdc.ProxyURL)
 	if err != nil {
 		return nil, fmt.Errorf("cannot create HTTP client for %q: %w", apiServer, err)
 	}

lib/promscrape/discovery/kubernetes/kubernetes.go

@@ -3,8 +3,8 @@ package kubernetes
 import (
 	"fmt"
 
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promauth"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/proxy"
 )
 
 // SDConfig represents kubernetes-based service discovery config.
@@ -16,7 +16,7 @@ type SDConfig struct {
 	BasicAuth       *promauth.BasicAuthConfig `yaml:"basic_auth,omitempty"`
 	BearerToken     string                    `yaml:"bearer_token,omitempty"`
 	BearerTokenFile string                    `yaml:"bearer_token_file,omitempty"`
-	ProxyURL        netutil.ProxyURL          `yaml:"proxy_url,omitempty"`
+	ProxyURL        proxy.URL                 `yaml:"proxy_url,omitempty"`
 	TLSConfig       *promauth.TLSConfig       `yaml:"tls_config,omitempty"`
 	Namespaces      Namespaces                `yaml:"namespaces,omitempty"`
 	Selectors       []Selector                `yaml:"selectors,omitempty"`

lib/promscrape/discoveryutils/client.go

@@ -6,13 +6,12 @@ import (
 	"fmt"
 	"net"
 	"net/http"
-	"net/url"
 	"strings"
 	"sync"
 	"time"
 
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promauth"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/proxy"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/timerpool"
 	"github.com/VictoriaMetrics/fasthttp"
 )
@@ -46,7 +45,7 @@ type Client struct {
 }
 
 // NewClient returns new Client for the given apiServer and the given ac.
-func NewClient(apiServer string, ac *promauth.Config, proxyURL *url.URL) (*Client, error) {
+func NewClient(apiServer string, ac *promauth.Config, proxyURL proxy.URL) (*Client, error) {
 	var (
 		dialFunc fasthttp.DialFunc
 		tlsCfg   *tls.Config
@@ -63,12 +62,6 @@ func NewClient(apiServer string, ac *promauth.Config, proxyURL *url.URL) (*Clien
 			return net.Dial("unix", dialAddr)
 		}
 	}
-	if proxyURL != nil {
-		dialFunc, err = netutil.GetProxyDialFunc(proxyURL)
-		if err != nil {
-			return nil, err
-		}
-	}
 
 	hostPort := string(u.Host())
 	isTLS := string(u.Scheme()) == "https"
@@ -82,10 +75,15 @@ func NewClient(apiServer string, ac *promauth.Config, proxyURL *url.URL) (*Clien
 		}
 		hostPort = net.JoinHostPort(hostPort, port)
 	}
+	if dialFunc == nil {
+		dialFunc, err = proxyURL.NewDialFunc(tlsCfg)
+		if err != nil {
+			return nil, err
+		}
+	}
 	hc := &fasthttp.HostClient{
 		Addr:                hostPort,
 		Name:                "vm_promscrape/discovery",
-		DialDualStack:       netutil.TCP6Enabled(),
 		IsTLS:               isTLS,
 		TLSConfig:           tlsCfg,
 		ReadTimeout:         time.Minute,
@@ -97,7 +95,6 @@ func NewClient(apiServer string, ac *promauth.Config, proxyURL *url.URL) (*Clien
 	blockingClient := &fasthttp.HostClient{
 		Addr:                hostPort,
 		Name:                "vm_promscrape/discovery",
-		DialDualStack:       netutil.TCP6Enabled(),
 		IsTLS:               isTLS,
 		TLSConfig:           tlsCfg,
 		ReadTimeout:         BlockingClientReadTimeout,

lib/promscrape/scrapework.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"math"
 	"math/bits"
-	"net/url"
 	"strconv"
 	"strings"
 	"sync"
@@ -18,6 +17,7 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promrelabel"
 	parser "github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/prometheus"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/proxy"
 	"github.com/VictoriaMetrics/metrics"
 	xxhash "github.com/cespare/xxhash/v2"
 )
@@ -72,7 +72,7 @@ type ScrapeWork struct {
 	AuthConfig *promauth.Config
 
 	// ProxyURL HTTP proxy url
-	ProxyURL *url.URL
+	ProxyURL proxy.URL
 
 	// Optional `metric_relabel_configs`.
 	MetricRelabelConfigs []promrelabel.ParsedRelabelConfig

lib/promscrape/statconn.go

@@ -2,14 +2,15 @@ package promscrape
 
 import (
 	"context"
+	"crypto/tls"
 	"fmt"
 	"net"
-	"net/url"
 	"sync"
 	"sync/atomic"
 	"time"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/proxy"
 	"github.com/VictoriaMetrics/fasthttp"
 	"github.com/VictoriaMetrics/metrics"
 )
@@ -48,18 +49,13 @@ var (
 	stdDialerOnce sync.Once
 )
 
-func getDialStatConn(proxyURL *url.URL) fasthttp.DialFunc {
+func newStatDialFunc(proxyURL proxy.URL, tlsConfig *tls.Config) (fasthttp.DialFunc, error) {
-	auth := netutil.MakeBasicAuthHeader(nil, proxyURL)
+	dialFunc, err := proxyURL.NewDialFunc(tlsConfig)
-	return func(addr string) (conn net.Conn, err error) {
+	if err != nil {
-		dialAddr := addr
+		return nil, err
-		if proxyURL != nil {
+	}
-			dialAddr = proxyURL.Host
+	statDialFunc := func(addr string) (net.Conn, error) {
-		}
+		conn, err := dialFunc(addr)
-		if netutil.TCP6Enabled() {
-			conn, err = fasthttp.DialDualStack(dialAddr)
-		} else {
-			conn, err = fasthttp.Dial(dialAddr)
-		}
 		dialsTotal.Inc()
 		if err != nil {
 			dialErrors.Inc()
@@ -69,17 +65,12 @@ func getDialStatConn(proxyURL *url.URL) fasthttp.DialFunc {
 			return nil, err
 		}
 		conns.Inc()
-		if proxyURL != nil {
-			if err := netutil.MakeProxyConnectCall(conn, []byte(addr), auth); err != nil {
-				_ = conn.Close()
-				return nil, err
-			}
-		}
 		sc := &statConn{
 			Conn: conn,
 		}
 		return sc, nil
 	}
+	return statDialFunc, nil
 }
 
 var (

lib/proxy/proxy.go

@@ -0,0 +1,117 @@
+package proxy
+
+import (
+	"bufio"
+	"crypto/tls"
+	"encoding/base64"
+	"fmt"
+	"net"
+	"net/url"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
+	"github.com/VictoriaMetrics/fasthttp"
+)
+
+// URL implements YAML.Marshaler and yaml.Unmarshaler interfaces for url.URL.
+type URL struct {
+	url *url.URL
+}
+
+// URL return the underlying url.
+func (u *URL) URL() *url.URL {
+	if u == nil || u.url == nil {
+		return nil
+	}
+	return u.url
+}
+
+// MarshalYAML implements yaml.Marshaler interface.
+func (u *URL) MarshalYAML() (interface{}, error) {
+	if u.url == nil {
+		return nil, nil
+	}
+	return u.url.String(), nil
+}
+
+// UnmarshalYAML implements yaml.Unmarshaler interface.
+func (u *URL) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var s string
+	if err := unmarshal(&s); err != nil {
+		return err
+	}
+	parsedURL, err := url.Parse(s)
+	if err != nil {
+		return fmt.Errorf("cannot parse proxy_url=%q as *url.URL: %w", s, err)
+	}
+	u.url = parsedURL
+	return nil
+}
+
+// NewDialFunc returns dial func for the given pu and tlsConfig.
+func (u *URL) NewDialFunc(tlsConfig *tls.Config) (fasthttp.DialFunc, error) {
+	if u == nil || u.url == nil {
+		return defaultDialFunc, nil
+	}
+	pu := u.url
+	if pu.Scheme != "http" && pu.Scheme != "https" {
+		return nil, fmt.Errorf("unknown scheme=%q for proxy_url=%q, must be http or https", pu.Scheme, pu)
+	}
+	var authHeader string
+	if pu.User != nil && len(pu.User.Username()) > 0 {
+		userPasswordEncoded := base64.StdEncoding.EncodeToString([]byte(pu.User.String()))
+		authHeader = "Proxy-Authorization: Basic " + userPasswordEncoded + "\r\n"
+	}
+	dialFunc := func(addr string) (net.Conn, error) {
+		proxyConn, err := defaultDialFunc(pu.Host)
+		if err != nil {
+			return nil, fmt.Errorf("cannot connect to proxy %q: %w", pu, err)
+		}
+		if pu.Scheme == "https" {
+			proxyConn = tls.Client(proxyConn, tlsConfig)
+		}
+		conn, err := sendConnectRequest(proxyConn, addr, authHeader)
+		if err != nil {
+			_ = proxyConn.Close()
+			return nil, fmt.Errorf("error when sending CONNECT request to proxy %q: %w", pu, err)
+		}
+		return conn, nil
+	}
+	return dialFunc, nil
+}
+
+func defaultDialFunc(addr string) (net.Conn, error) {
+	if netutil.TCP6Enabled() {
+		return fasthttp.DialDualStack(addr)
+	}
+	return fasthttp.Dial(addr)
+}
+
+// sendConnectRequest sends CONNECT request to proxyConn for the given addr and authHeader and returns the established connection to dstAddr.
+func sendConnectRequest(proxyConn net.Conn, dstAddr, authHeader string) (net.Conn, error) {
+	req := "CONNECT " + dstAddr + " HTTP/1.1\r\nHost: " + dstAddr + "\r\n" + authHeader + "\r\n"
+	if _, err := proxyConn.Write([]byte(req)); err != nil {
+		return nil, fmt.Errorf("cannot send CONNECT request for dstAddr=%q: %w", dstAddr, err)
+	}
+	var res fasthttp.Response
+	res.SkipBody = true
+	conn := &bufferedReaderConn{
+		br:   bufio.NewReader(proxyConn),
+		Conn: proxyConn,
+	}
+	if err := res.Read(conn.br); err != nil {
+		return nil, fmt.Errorf("cannot read CONNECT response for dstAddr=%q: %w", dstAddr, err)
+	}
+	if statusCode := res.Header.StatusCode(); statusCode != 200 {
+		return nil, fmt.Errorf("unexpected status code received: %d; want: 200", statusCode)
+	}
+	return conn, nil
+}
+
+type bufferedReaderConn struct {
+	net.Conn
+	br *bufio.Reader
+}
+
+func (brc *bufferedReaderConn) Read(p []byte) (int, error) {
+	return brc.br.Read(p)
+}