.forgejo/workflows/dco.yml

@@ -1,21 +0,0 @@
-name: DCO action
-on: [pull_request]
-
-jobs:
-  dco:
-    name: DCO
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-        with:
-          fetch-depth: 0
-
-      - name: Setup Go
-        uses: actions/setup-go@v3
-        with:
-          go-version: '1.23'
-
-      - name: Run commit format checker
-        uses: https://git.frostfs.info/TrueCloudLab/dco-go@v3
-        with:
-          from: 'origin/${{ github.event.pull_request.base.ref }}'

.forgejo/workflows/pre-commit.yml

@@ -1,25 +0,0 @@
-name: Pre-commit hooks
-on: [pull_request]
-
-jobs:
-  precommit:
-    name: Pre-commit
-    env:
-      # Skip pre-commit hooks which are executed by other actions.
-      SKIP: make-lint,go-staticcheck-repo-mod,go-unit-tests,gofumpt
-    runs-on: ubuntu-22.04
-    # If we use actions/setup-python from either Github or Gitea,
-    # the line above fails with a cryptic error about not being able to find python.
-    # So install everything manually.
-    steps:
-      - uses: actions/checkout@v3
-      - name: Set up Go
-        uses: actions/setup-go@v3
-        with:
-          go-version: 1.23
-      - name: Set up Python
-        run: |
-          apt update
-          apt install -y pre-commit
-      - name: Run pre-commit
-        run: pre-commit run --color=always --hook-stage manual --all-files

.forgejo/workflows/tests.yml

@@ -1,111 +0,0 @@
-name: Tests and linters
-on: [pull_request]
-
-jobs:
-  lint:
-    name: Lint
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-
-      - name: Set up Go
-        uses: actions/setup-go@v3
-        with:
-          go-version: '1.23'
-          cache: true
-
-      - name: Install linters
-        run: make lint-install
-
-      - name: Run linters
-        run: make lint
-
-  tests:
-    name: Tests
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        go_versions: [ '1.22', '1.23' ]
-      fail-fast: false
-    steps:
-      - uses: actions/checkout@v3
-
-      - name: Set up Go
-        uses: actions/setup-go@v3
-        with:
-          go-version: '${{ matrix.go_versions }}'
-          cache: true
-
-      - name: Run tests
-        run: make test
-
-  tests-race:
-    name: Tests with -race
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-
-      - name: Set up Go
-        uses: actions/setup-go@v3
-        with:
-          go-version: '1.23'
-          cache: true
-
-      - name: Run tests
-        run: go test ./... -count=1 -race
-
-  staticcheck:
-    name: Staticcheck
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-
-      - name: Set up Go
-        uses: actions/setup-go@v3
-        with:
-          go-version: '1.23'
-          cache: true
-
-      - name: Install staticcheck
-        run: make staticcheck-install
-
-      - name: Run staticcheck
-        run: make staticcheck-run
-
-  gopls:
-    name: gopls check
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-
-      - name: Set up Go
-        uses: actions/setup-go@v3
-        with:
-          go-version: '1.23'
-          cache: true
-
-      - name: Install gopls
-        run: make gopls-install
-
-      - name: Run gopls
-        run: make gopls-run
-
-  fumpt:
-    name: Run gofumpt
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-
-      - name: Set up Go
-        uses: actions/setup-go@v3
-        with:
-          go-version: '1.23'
-          cache: true
-
-      - name: Install gofumpt
-        run: make fumpt-install
-
-      - name: Run gofumpt
-        run: |
-          make fumpt
-          git diff --exit-code --quiet

.forgejo/workflows/vulncheck.yml

@@ -1,22 +0,0 @@
-name: Vulncheck
-on: [pull_request]
-
-jobs:
-  vulncheck:
-    name: Vulncheck
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-        with:
-          fetch-depth: 0
-
-      - name: Setup Go
-        uses: actions/setup-go@v3
-        with:
-          go-version: '1.23.5'
-
-      - name: Install govulncheck
-        run: go install golang.org/x/vuln/cmd/govulncheck@latest
-
-      - name: Run govulncheck
-        run: govulncheck ./...

.gitattributes

@@ -1 +0,0 @@
-/go.sum -diff

.gitignore

@@ -1,22 +0,0 @@
-# IDE
-.idea
-.vscode
-
-# Vendoring
-vendor
-
-# tempfiles
-.DS_Store
-*~
-.cache
-
-temp
-tmp
-
-# binary
-bin/
-release/
-
-# coverage
-coverage.txt
-coverage.html

.golangci.yml

@@ -1,75 +0,0 @@
-# This file contains all available configuration options
-# with their default values.
-
-# options for analysis running
-run:
-  # timeout for analysis, e.g. 30s, 5m, default is 1m
-  timeout: 20m
-
-  # include test files or not, default is true
-  tests: false
-
-# output configuration options
-output:
-  # colored-line-number|line-number|json|tab|checkstyle|code-climate, default is "colored-line-number"
-  formats:
-    - format: tab
-
-# all available settings of specific linters
-linters-settings:
-  exhaustive:
-    # indicates that switch statements are to be considered exhaustive if a
-    # 'default' case is present, even if all enum members aren't listed in the
-    # switch
-    default-signifies-exhaustive: true
-  govet:
-    # report about shadowed variables
-    check-shadowing: false
-  staticcheck:
-    checks: ["all", "-SA1019"] # TODO Enable SA1019 after deprecated warning are fixed.
-  funlen:
-    lines: 80 # default 60
-    statements: 60 # default 40
-  gocognit:
-    min-complexity: 40 # default 30
-  unused:
-    field-writes-are-uses: false
-    exported-fields-are-used: false
-    local-variables-are-used: false
-
-linters:
-  enable:
-    # mandatory linters
-    - govet
-    - revive
-
-    # some default golangci-lint linters
-    - errcheck
-    - gosimple
-    - godot
-    - ineffassign
-    - staticcheck
-    - typecheck
-    - unused
-
-    # extra linters
-    - bidichk
-    - durationcheck
-    - exhaustive
-    - copyloopvar
-    - gofmt
-    - goimports
-    - misspell
-    - predeclared
-    - reassign
-    - whitespace
-    - containedctx
-    - funlen
-    - gocognit
-    - contextcheck
-    - importas
-    - perfsprint
-    - testifylint
-    - protogetter
-  disable-all: true
-  fast: false

.pre-commit-config.yaml

@@ -1,56 +0,0 @@
-ci:
-  autofix_prs: false
-
-repos:
-  - repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v4.5.0
-    hooks:
-    - id: check-added-large-files
-    - id: check-case-conflict
-    - id: check-executables-have-shebangs
-    - id: check-shebang-scripts-are-executable
-    - id: check-merge-conflict
-    - id: check-json
-    - id: check-xml
-    - id: check-yaml
-    - id: trailing-whitespace
-      args: [--markdown-linebreak-ext=md]
-    - id: end-of-file-fixer
-      exclude: "(.key|.svg)$"
-
-  - repo: https://github.com/shellcheck-py/shellcheck-py
-    rev: v0.9.0.6
-    hooks:
-      - id: shellcheck
-
-  - repo: local
-    hooks:
-      - id: make-lint
-        name: Run Make Lint
-        entry: make lint
-        language: system
-        pass_filenames: false
-
-  - repo: local
-    hooks:
-       - id: go-unit-tests
-         name: go unit tests
-         entry: make test GOFLAGS=''
-         pass_filenames: false
-         types: [go]
-         language: system
-
-  - repo: local
-    hooks:
-       - id: gofumpt
-         name: gofumpt
-         entry: make fumpt
-         pass_filenames: false
-         types: [go]
-         language: system
-
-  - repo: https://github.com/TekWizely/pre-commit-golang
-    rev: v1.0.0-rc.1
-    hooks:
-       - id: go-staticcheck-repo-mod
-       - id: go-mod-tidy

CODEOWNERS

@@ -1,3 +0,0 @@
-.*          @TrueCloudLab/storage-core-committers @TrueCloudLab/storage-core-developers
-.forgejo/.* @potyarkin
-Makefile    @potyarkin

Makefile

@@ -1,82 +1,9 @@
-#!/usr/bin/make -f
+integration-test:
-
+	# TODO figure out needed capabilities
-STATICCHECK_VERSION ?= 2024.1.1
+	sudo go test -count=1 -v ./... -tags=integration
-LINT_VERSION ?= 1.60.3
-
-BIN = bin
-OUTPUT_LINT_DIR ?= $(abspath $(BIN))/linters
-LINT_DIR = $(OUTPUT_LINT_DIR)/golangci-lint-$(LINT_VERSION)
-TMP_DIR := .cache
-
-STATICCHECK_DIR ?= $(abspath $(BIN))/staticcheck
-STATICCHECK_VERSION_DIR ?= $(STATICCHECK_DIR)/$(STATICCHECK_VERSION)
-
-GOFUMPT_VERSION ?= v0.7.0
-GOFUMPT_DIR ?= $(abspath $(BIN))/gofumpt
-GOFUMPT_VERSION_DIR ?= $(GOFUMPT_DIR)/$(GOFUMPT_VERSION)
-
-GOPLS_VERSION ?= v0.16.2
-GOPLS_DIR ?= $(abspath $(BIN))/gopls
-GOPLS_VERSION_DIR ?= $(GOPLS_DIR)/$(GOPLS_VERSION)
-GOPLS_TEMP_FILE := $(shell mktemp)
 
 test:
 	go test -count=1 -v ./...
 
-# Install linters
+patch-example:
-lint-install:
+	gopatch -d -p ./multinet.patch ./testdata/patch*
-	@rm -rf $(OUTPUT_LINT_DIR)
-	@mkdir -p $(OUTPUT_LINT_DIR)
-	@CGO_ENABLED=1 GOBIN=$(LINT_DIR) go install -trimpath github.com/golangci/golangci-lint/cmd/golangci-lint@v$(LINT_VERSION)
-
-# Run linters
-lint:
-	@if [ ! -d "$(LINT_DIR)" ]; then \
-		make lint-install; \
-	fi
-	$(LINT_DIR)/golangci-lint run
-
-# Install staticcheck
-staticcheck-install:
-	@rm -rf $(STATICCHECK_DIR)
-	@mkdir -p $(STATICCHECK_DIR)
-	@GOBIN=$(STATICCHECK_VERSION_DIR) go install honnef.co/go/tools/cmd/staticcheck@$(STATICCHECK_VERSION)
-
-# Run staticcheck
-staticcheck-run:
-	@if [ ! -d "$(STATICCHECK_VERSION_DIR)" ]; then \
-		make staticcheck-install; \
-	fi
-	@$(STATICCHECK_VERSION_DIR)/staticcheck ./...
-
-# Install gopls
-gopls-install:
-	@rm -rf $(GOPLS_DIR)
-	@mkdir -p $(GOPLS_DIR)
-	@GOBIN=$(GOPLS_VERSION_DIR) go install golang.org/x/tools/gopls@$(GOPLS_VERSION)
-
-# Run gopls
-gopls-run:
-	@if [ ! -d "$(GOPLS_VERSION_DIR)" ]; then \
-		make gopls-install; \
-	fi
-	$(GOPLS_VERSION_DIR)/gopls check $(SOURCES) 2>&1 >$(GOPLS_TEMP_FILE)
-	@if [[ $$(wc -l < $(GOPLS_TEMP_FILE)) -ne 0 ]]; then \
-		cat $(GOPLS_TEMP_FILE); \
-		exit 1; \
-	fi
-	rm $(GOPLS_TEMP_FILE)
-
-# Install gofumpt
-fumpt-install:
-	@rm -rf $(GOFUMPT_DIR)
-	@mkdir -p $(GOFUMPT_DIR)
-	@GOBIN=$(GOFUMPT_VERSION_DIR) go install mvdan.cc/gofumpt@$(GOFUMPT_VERSION)
-
-# Run gofumpt
-fumpt:
-	@if [ ! -d "$(GOFUMPT_VERSION_DIR)" ]; then \
-		make fumpt-install; \
-	fi
-	@echo "⇒ Processing gofumpt check"
-	$(GOFUMPT_VERSION_DIR)/gofumpt -l -w .

README.md

@@ -16,31 +16,10 @@ But sometimes you need to invent a bicycle.
 ## Usage
 
 ```golang
-import (
+import "git.frostfs.info/TrueCloudLab/multinet"
-    "context"
-    "net"
-    "net/netip"
-
-    "git.frostfs.info/TrueCloudLab/multinet"
-)
 
 d, err := multinet.NewDialer(Config{
-    Subnets:  []Subnet{
+    Subnets:  []string{"10.11.70.0/23", "192.168.123.0/24"},
-        {
-            Prefix: netip.MustParsePrefix("10.11.70.0/23"),
-            SourceIPs: []netip.Addr{
-                netip.MustParseAddr("10.11.70.42"),
-                netip.MustParseAddr("10.11.71.42"),
-            },
-        },
-        {
-            Prefix: netip.MustParsePrefix("192.168.123.0/24"),
-            SourceIPs: []netip.Addr{
-                netip.MustParseAddr("192.168.123.42"),
-                netip.MustParseAddr("192.168.123.142"),
-            },
-        },
-    },
     Balancer: multinet.BalancerTypeRoundRobin,
 })
 if err != nil {
@@ -53,3 +32,18 @@ if err != nil {
 }
 // do stuff
 ```
+
+### Updating interface state
+
+`Multidialer` exposes `UpdateInterface()` method for updating state of a single link.
+`NetlinkWatcher` can wrap `Multidialer` type and perform all updates automatically.
+
+TODO: describe needed capabilities here.
+
+## Patch
+
+To perform refactoring (use `multinet.Dial` instead of `net.Dial`) using [gopatch](https://github.com/uber-go/gopatch):
+
+```bash
+gopatch -p ./multinet.patch <project directory>
+```

balancer.go

@@ -3,7 +3,6 @@ package multinet
 import (
 	"context"
 	"errors"
-	"fmt"
 	"net"
 	"sync/atomic"
 )
@@ -19,8 +18,6 @@ const (
 	BalancerTypeRoundRobin BalancerType = "roundrobin"
 )
 
-var errNoSuitableNodeFound = errors.New("no suitale node found")
-
 type balancer interface {
 	DialContext(ctx context.Context, s *Subnet, network, address string) (net.Conn, error)
 }
@@ -32,13 +29,17 @@ type roundRobin struct {
 
 func (r *roundRobin) DialContext(ctx context.Context, s *Subnet, network, address string) (net.Conn, error) {
 	next := int(r.i.Add(1))
-	for i := range s.SourceIPs {
+	for i := range s.Interfaces {
-		ii := s.SourceIPs[(i+next)%len(s.SourceIPs)]
+		ii := s.Interfaces[(i+next)%len(s.Interfaces)]
-		dd := r.d.dialer
+		if ii.Down {
-		dd.LocalAddr = &net.TCPAddr{IP: net.IP(ii.AsSlice())}
+			continue
-		return r.d.dialContext(ctx, &dd, network, address)
 		}
-	return nil, fmt.Errorf("(*roundRobin).DialContext: %w", errNoSuitableNodeFound)
+
+		dd := r.d.dialer
+		dd.LocalAddr = ii.LocalAddr
+		return r.d.dialContext(&dd, ctx, network, address)
+	}
+	return nil, errors.New("(*roundRobin).DialContext: no suitale node found")
 }
 
 type firstEnabled struct {
@@ -46,11 +47,15 @@ type firstEnabled struct {
 }
 
 func (r *firstEnabled) DialContext(ctx context.Context, s *Subnet, network, address string) (net.Conn, error) {
-	for i := range s.SourceIPs {
+	for i := range s.Interfaces {
-		ii := s.SourceIPs[i]
+		ii := s.Interfaces[i%len(s.Interfaces)]
-		dd := r.d.dialer
+		if ii.Down {
-		dd.LocalAddr = &net.TCPAddr{IP: net.IP(ii.AsSlice())}
+			continue
-		return r.d.dialContext(ctx, &dd, network, address)
 		}
-	return nil, fmt.Errorf("(*firstEnabled).DialContext: %w", errNoSuitableNodeFound)
+
+		dd := r.d.dialer
+		dd.LocalAddr = ii.LocalAddr
+		return r.d.dialContext(&dd, ctx, network, address)
+	}
+	return nil, errors.New("(*firstEnabled).DialContext: no suitale node found")
 }

default.go

@@ -0,0 +1,31 @@
+package multinet
+
+import (
+	"context"
+	"fmt"
+	"net"
+)
+
+var (
+	defaultDialer    Multidialer
+	defaultDialerErr error
+)
+
+func init() {
+	var err error
+	defaultDialer, err = NewDialer(Config{
+		Balancer: BalancerTypeRoundRobin,
+		Subnets:  []string{"0.0.0.0/0", "::/0"},
+	})
+	if err != nil {
+		defaultDialerErr = fmt.Errorf("failed to initialize default dialier: %w", err)
+	}
+}
+
+// Dial dials provided network and address using default dialer.
+func Dial(network, address string) (net.Conn, error) {
+	if defaultDialerErr != nil {
+		return nil, defaultDialerErr
+	}
+	return defaultDialer.DialContext(context.Background(), network, address)
+}

default_test.go

@@ -0,0 +1,29 @@
+//go:build integration
+
+package multinet
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestDefaultDialer(t *testing.T) {
+	srv := startHTTP(t)
+	defer require.NoError(t, srv.Close())
+
+	conn, err := Dial("tcp", "localhost:8080")
+	require.NoError(t, err)
+	require.NoError(t, conn.Close())
+}
+
+func startHTTP(t *testing.T) *http.Server {
+	srv := &http.Server{Addr: ":8080"}
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { fmt.Fprintf(w, "Test stub") })
+	go func() {
+		require.ErrorIs(t, srv.ListenAndServe(), http.ErrServerClosed)
+	}()
+	return srv
+}

dialer.go

@@ -1,10 +1,12 @@
 package multinet
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"net"
 	"net/netip"
+	"sort"
 	"sync"
 	"time"
 )
@@ -18,6 +20,12 @@ type Dialer interface {
 	DialContext(ctx context.Context, network, address string) (net.Conn, error)
 }
 
+// Multidialer is like Dialer, but supports link state updates.
+type Multidialer interface {
+	Dialer
+	UpdateInterface(name string, addr netip.Addr, status bool) error
+}
+
 var (
 	_ Dialer = (*net.Dialer)(nil)
 	_ Dialer = (*dialer)(nil)
@@ -39,29 +47,30 @@ type dialer struct {
 	resolver net.Resolver
 	// See Config.FallbackDelay description.
 	fallbackDelay time.Duration
-	// Event handler.
-	eh EventHandler
 }
 
-// Subnet represents a single subnet, possibly routable from multiple source IPs.
+// Subnet represents a single subnet, possibly routable from multiple interfaces.
 type Subnet struct {
-	Prefix    netip.Prefix
+	Mask       netip.Prefix
-	SourceIPs []netip.Addr
+	Interfaces []Source
 }
 
-type EventHandler interface {
+// Source represents a single source IP belonging to a particular subnet.
-	DialPerformed(sourceIP net.Addr, network, address string, err error)
+type Source struct {
+	Name      string
+	LocalAddr *net.TCPAddr
+	Down      bool
 }
 
 // Config contains Multidialer configuration.
 type Config struct {
-	// Routable subnets.
+	// Routable subnets to prioritize in CIDR format.
-	Subnets []Subnet
+	Subnets []string
 	// If true, the only configurd subnets available through this dialer.
 	// Otherwise, a failback to the net.DefaultDialer.
 	Restrict bool
-	// Dialer contains default options for the net.Dialer to use.
+	// Dialer containes default options for the net.Dialer to use.
-	// LocalAddr is overridden.
+	// LocalAddr is overriden.
 	Dialer net.Dialer
 	// Balancer specifies algorithm used to pick source address.
 	Balancer BalancerType
@@ -74,17 +83,47 @@ type Config struct {
 	// If zero, a default delay of 300ms is used.
 	// A negative value disables Fast Fallback support.
 	FallbackDelay time.Duration
+	// InterfaceSource is custom `Interface`` source.
+	// If not specified, default implementation is used (`net.Interfaces()``).
+	InterfaceSource func() ([]Interface, error)
 	// DialContext is custom DialContext function.
 	// If not specified, default implemenattion is used (`d.DialContext(ctx, network, address)`).
 	DialContext func(d *net.Dialer, ctx context.Context, network, address string) (net.Conn, error)
-	// EventHandler defines event handler.
-	EventHandler EventHandler
 }
 
 // NewDialer ...
-func NewDialer(c Config) (Dialer, error) {
+func NewDialer(c Config) (Multidialer, error) {
+	var ifaces []Interface
+	var err error
+	if c.InterfaceSource != nil {
+		ifaces, err = c.InterfaceSource()
+	} else {
+		ifaces, err = systemInterfaces()
+	}
+	if err != nil {
+		return nil, err
+	}
+	sort.Slice(ifaces, func(i, j int) bool {
+		return ifaces[i].Name() < ifaces[j].Name()
+	})
+
+	var sources []iface
+	for i := range ifaces {
+		info, err := processIface(ifaces[i])
+		if err != nil {
+			return nil, err
+		}
+		sources = append(sources, info)
+	}
+
 	var d dialer
-	d.subnets = c.Subnets
+	for _, subnet := range c.Subnets {
+		s, err := processSubnet(subnet, sources)
+		if err != nil {
+			return nil, err
+		}
+		d.subnets = append(d.subnets, s)
+	}
 
 	switch c.Balancer {
 	case BalancerTypeNoop:
@@ -106,20 +145,69 @@ func NewDialer(c Config) (Dialer, error) {
 		d.customDialContext = c.DialContext
 	}
 
-	if c.EventHandler != nil {
+	return &d, nil
-		d.eh = c.EventHandler
+}
-	} else {
+
-		d.eh = noopEventHandler{}
+type iface struct {
+	name  string
+	addrs []netip.Prefix
+}
+
+func processIface(info Interface) (iface, error) {
+	ips, err := info.Addrs()
+	if err != nil {
+		return iface{}, err
 	}
 
-	return &d, nil
+	var addrs []netip.Prefix
+	for i := range ips {
+		p, err := netip.ParsePrefix(ips[i].String())
+		if err != nil {
+			return iface{}, err
+		}
+
+		addrs = append(addrs, p)
+	}
+	return iface{name: info.Name(), addrs: addrs}, nil
+}
+
+func processSubnet(subnet string, sources []iface) (Subnet, error) {
+	s, err := netip.ParsePrefix(subnet)
+	if err != nil {
+		return Subnet{}, err
+	}
+
+	var ifs []Source
+	for _, source := range sources {
+		for i := range source.addrs {
+			src := source.addrs[i].Addr()
+			if s.Contains(src) {
+				ifs = append(ifs, Source{
+					Name:      source.name,
+					LocalAddr: &net.TCPAddr{IP: net.IP(src.AsSlice())},
+				})
+			}
+		}
+	}
+
+	sort.Slice(ifs, func(i, j int) bool {
+		if ifs[i].Name != ifs[j].Name {
+			return ifs[i].Name < ifs[j].Name
+		}
+		return bytes.Compare(ifs[i].LocalAddr.IP, ifs[j].LocalAddr.IP) == -1
+	})
+
+	return Subnet{
+		Mask:       s,
+		Interfaces: ifs,
+	}, nil
 }
 
 // DialContext implements the Dialer interface.
 // Hostnames for address are currently not supported.
 func (d *dialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
 	addr, err := netip.ParseAddrPort(address)
-	if err != nil { // try resolve as hostname
+	if err != nil { //try resolve as hostname
 		return d.dialContextHostname(ctx, network, address)
 	}
 	return d.dialAddr(ctx, network, address, addr)
@@ -281,7 +369,7 @@ func (d *dialer) dialAddr(ctx context.Context, network, address string, addr net
 	defer d.mtx.RUnlock()
 
 	for i := range d.subnets {
-		if d.subnets[i].Prefix.Contains(addr.Addr()) {
+		if d.subnets[i].Mask.Contains(addr.Addr()) {
 			return d.balancer.DialContext(ctx, &d.subnets[i], network, address)
 		}
 	}
@@ -289,19 +377,38 @@ func (d *dialer) dialAddr(ctx context.Context, network, address string, addr net
 	if d.restrict {
 		return nil, fmt.Errorf("no suitable interface for: [%s]%s", network, address)
 	}
-	return d.dialContext(ctx, &d.dialer, network, address)
+	return d.dialContext(&d.dialer, ctx, network, address)
 }
 
-func (d *dialer) dialContext(ctx context.Context, nd *net.Dialer, network, address string) (net.Conn, error) {
+func (d *dialer) dialContext(nd *net.Dialer, ctx context.Context, network, address string) (net.Conn, error) {
-	var conn net.Conn
-	var err error
 	if h := d.customDialContext; h != nil {
-		conn, err = h(nd, ctx, network, address)
+		return h(nd, ctx, network, address)
-	} else {
-		conn, err = nd.DialContext(ctx, network, address)
 	}
-	d.eh.DialPerformed(nd.LocalAddr, network, address, err)
+	return nd.DialContext(ctx, network, address)
-	return conn, err
+}
+
+// UpdateInterface implements the Multidialer interface.
+// Updating address on a specific interface is currently not supported.
+func (d *dialer) UpdateInterface(iface string, addr netip.Addr, up bool) error {
+	d.mtx.Lock()
+	defer d.mtx.Unlock()
+
+	for i := range d.subnets {
+		for j := range d.subnets[i].Interfaces {
+			matchIface := d.subnets[i].Interfaces[j].Name == iface
+			if matchIface {
+				d.subnets[i].Interfaces[j].Down = !up
+				continue
+			}
+
+			a, _ := netip.AddrFromSlice(d.subnets[i].Interfaces[j].LocalAddr.IP)
+			matchAddr := a.IsUnspecified() || addr == a
+			if matchAddr {
+				d.subnets[i].Interfaces[j].Down = !up
+			}
+		}
+	}
+	return nil
 }
 
 // splitByType divides an address list into two categories:
@@ -321,7 +428,3 @@ func splitByType(addrs []netip.AddrPort) (primaries []netip.AddrPort, fallbacks
 	}
 	return
 }
-
-type noopEventHandler struct{}
-
-func (s noopEventHandler) DialPerformed(net.Addr, string, string, error) {}

dialer_hostname_test.go

@@ -3,7 +3,6 @@ package multinet
 import (
 	"context"
 	"net"
-	"net/netip"
 	"testing"
 	"time"
 
@@ -15,15 +14,8 @@ func TestHostnameResolveIPv4(t *testing.T) {
 	resolvedAddr := "10.11.12.180:8080"
 	resolved := false
 	d, err := NewDialer(Config{
-		Subnets: []Subnet{
+		Subnets:         []string{"10.11.12.0/24"},
-			{
+		InterfaceSource: testInterfacesV4,
-				Prefix: netip.MustParsePrefix("10.11.12.0/24"),
-				SourceIPs: []netip.Addr{
-					netip.MustParseAddr("10.11.12.101"),
-					netip.MustParseAddr("10.11.12.102"),
-				},
-			},
-		},
 		DialContext: func(d *net.Dialer, ctx context.Context, network, address string) (net.Conn, error) {
 			if resolvedAddr == address {
 				resolved = true
@@ -50,15 +42,8 @@ func TestHostnameResolveIPv6(t *testing.T) {
 	ipv6 := net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:8195")
 	resolved := false
 	d, err := NewDialer(Config{
-		Subnets: []Subnet{
+		Subnets:         []string{"2001:db8:85a3:8d3::/64"},
-			{
+		InterfaceSource: testInterfacesV6,
-				Prefix: netip.MustParsePrefix("2001:db8:85a3:8d3::/64"),
-				SourceIPs: []netip.Addr{
-					netip.MustParseAddr("2001:db8:85a3:8d3:1319:8a2e:370:7348"),
-					netip.MustParseAddr("2001:db8:85a3:8d3:1319:8a2e:370:8192"),
-				},
-			},
-		},
 		DialContext: func(d *net.Dialer, ctx context.Context, network, address string) (net.Conn, error) {
 			if resolvedAddr == address {
 				resolved = true
@@ -80,6 +65,68 @@ func TestHostnameResolveIPv6(t *testing.T) {
 	require.True(t, resolved)
 }
 
+func testInterfacesV4() ([]Interface, error) {
+	return []Interface{
+		&testInterface{
+			name: "data1",
+			addrs: []net.Addr{
+				&testAddr{
+					network: "tcp",
+					str:     "10.11.12.101/24",
+				},
+			},
+		},
+		&testInterface{
+			name: "data2",
+			addrs: []net.Addr{
+				&testAddr{
+					network: "tcp",
+					str:     "10.11.12.102/24",
+				},
+			},
+		},
+	}, nil
+}
+
+func testInterfacesV6() ([]Interface, error) {
+	return []Interface{
+		&testInterface{
+			name: "data1",
+			addrs: []net.Addr{
+				&testAddr{
+					network: "tcp",
+					str:     "2001:db8:85a3:8d3:1319:8a2e:370:7348/64",
+				},
+			},
+		},
+		&testInterface{
+			name: "data2",
+			addrs: []net.Addr{
+				&testAddr{
+					network: "tcp",
+					str:     "2001:db8:85a3:8d3:1319:8a2e:370:8192/64",
+				},
+			},
+		},
+	}, nil
+}
+
+type testInterface struct {
+	name  string
+	addrs []net.Addr
+}
+
+func (i *testInterface) Name() string               { return i.name }
+func (i *testInterface) Addrs() ([]net.Addr, error) { return i.addrs, nil }
+
+type testAddr struct {
+	network string
+	str     string
+}
+
+func (a *testAddr) Network() string { return a.network }
+func (a *testAddr) String() string  { return a.str }
+
 type testDnsConn struct {
 	wantName   string
 	ipv4       []byte

dialer_integration_test.go

@@ -0,0 +1,166 @@
+//go:build integration
+
+package multinet
+
+import (
+	"net"
+	"net/netip"
+	"runtime"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"github.com/vishvananda/netlink"
+	"github.com/vishvananda/netns"
+)
+
+func TestDialer(t *testing.T) {
+	runInNewNamespace(t, "2 interfaces with multiple routes in different subnets", func(t *testing.T, ns netns.NsHandle) {
+		setup(t, map[string][]string{
+			"testdev1": {"1.2.30.10/23", "4.4.4.4/8"},
+			"testdev2": {"1.2.30.11/23", "4.4.4.5/8"},
+		})
+
+		// Do not use `t.Run` because everything should be executed in a single OS thread.
+
+		{ // Restrict to a single subnet.
+			d, err := NewDialer(Config{
+				Subnets: []string{"1.2.30.0/23"},
+			})
+			require.NoError(t, err)
+			require.Equal(t, []Subnet{
+				{
+					Mask: netip.MustParsePrefix("1.2.30.0/23"),
+					Interfaces: []Source{
+						{Name: "testdev1", LocalAddr: &net.TCPAddr{IP: net.IP{1, 2, 30, 10}}},
+						{Name: "testdev2", LocalAddr: &net.TCPAddr{IP: net.IP{1, 2, 30, 11}}},
+					},
+				},
+			}, d.(*dialer).subnets)
+		}
+
+		{ // Restrict to two subnets.
+			d, err := NewDialer(Config{
+				Subnets: []string{"1.2.30.0/23", "4.0.0.0/8"},
+			})
+			require.NoError(t, err)
+			require.Equal(t, []Subnet{
+				{
+					Mask: netip.MustParsePrefix("1.2.30.0/23"),
+					Interfaces: []Source{
+						{Name: "testdev1", LocalAddr: &net.TCPAddr{IP: net.IP{1, 2, 30, 10}}},
+						{Name: "testdev2", LocalAddr: &net.TCPAddr{IP: net.IP{1, 2, 30, 11}}},
+					},
+				},
+				{
+					Mask: netip.MustParsePrefix("4.0.0.0/8"),
+					Interfaces: []Source{
+						{Name: "testdev1", LocalAddr: &net.TCPAddr{IP: net.IP{4, 4, 4, 4}}},
+						{Name: "testdev2", LocalAddr: &net.TCPAddr{IP: net.IP{4, 4, 4, 5}}},
+					},
+				},
+			}, d.(*dialer).subnets)
+		}
+	})
+	runInNewNamespace(t, "4 interfaces, 2 for data, 2 internal", func(t *testing.T, ns netns.NsHandle) {
+		setup(t, map[string][]string{
+			"internal1": {"192.168.0.1/16"},
+			"internal2": {"192.168.0.2/16"},
+			"data1":     {"10.11.12.101/24"},
+			"data2":     {"10.11.12.102/24"},
+		})
+
+		d, err := NewDialer(Config{
+			Subnets: []string{"10.11.12.0/24", "192.168.0.0/16"},
+		})
+		require.NoError(t, err)
+		require.Equal(t, []Subnet{
+			{
+				Mask: netip.MustParsePrefix("10.11.12.0/24"),
+				Interfaces: []Source{
+					{Name: "data1", LocalAddr: &net.TCPAddr{IP: net.IP{10, 11, 12, 101}}},
+					{Name: "data2", LocalAddr: &net.TCPAddr{IP: net.IP{10, 11, 12, 102}}},
+				},
+			},
+			{
+				Mask: netip.MustParsePrefix("192.168.0.0/16"),
+				Interfaces: []Source{
+					{Name: "internal1", LocalAddr: &net.TCPAddr{IP: net.IP{192, 168, 0, 1}}},
+					{Name: "internal2", LocalAddr: &net.TCPAddr{IP: net.IP{192, 168, 0, 2}}},
+				},
+			},
+		}, d.(*dialer).subnets)
+	})
+	runInNewNamespace(t, "with ipv6", func(t *testing.T, ns netns.NsHandle) {
+		addr1 := "2001:db8:85a3:8d3:1319:8a2e:370:7348/64"
+		addr2 := "2001:db8:85a3:8d3:1319:8a2e:370:8192/64"
+		setup(t, map[string][]string{
+			"testdev1": {addr1},
+			"testdev2": {addr2},
+		})
+
+		// Do not use `t.Run` because everything should be executed in a single OS thread.
+
+		{ // Restrict to a single subnet.
+			d, err := NewDialer(Config{
+				Subnets: []string{"2001:db8:85a3:8d3::/64"},
+			})
+			require.NoError(t, err)
+			require.Equal(t, []Subnet{
+				{
+					Mask: netip.MustParsePrefix("2001:db8:85a3:8d3::/64"),
+					Interfaces: []Source{
+						{Name: "testdev1", LocalAddr: mustParseIPv6(t, addr1)},
+						{Name: "testdev2", LocalAddr: mustParseIPv6(t, addr2)},
+					},
+				},
+			}, d.(*dialer).subnets)
+		}
+	})
+}
+
+func mustParseIPv6(t *testing.T, s string) *net.TCPAddr {
+	ip, _, err := net.ParseCIDR(s)
+	require.NoError(t, err)
+	return &net.TCPAddr{IP: ip}
+}
+
+func setup(t *testing.T, config map[string][]string) {
+	for name, ips := range config {
+		link := createLink(t, name)
+		for i := range ips {
+			ip, err := netlink.ParseIPNet(ips[i])
+			require.NoError(t, err)
+			require.NoError(t, netlink.AddrAdd(link, &netlink.Addr{IPNet: ip}))
+		}
+	}
+}
+
+func createLink(t *testing.T, name string) netlink.Link {
+	require.NoError(t, netlink.LinkAdd(&netlink.Dummy{LinkAttrs: netlink.LinkAttrs{Name: name}}))
+
+	link, err := netlink.LinkByName(name)
+	require.NoError(t, err)
+	require.NoError(t, netlink.LinkSetUp(link))
+	return link
+}
+
+func runInNewNamespace(t *testing.T, name string, f func(t *testing.T, ns netns.NsHandle)) {
+	t.Run(name, func(t *testing.T) {
+		// To avoid messing with host network settings,
+		// we create a new names space and execute tests in it.
+		// Switching thread can move us to a different namespace, thus this line.
+		runtime.LockOSThread()
+		defer runtime.UnlockOSThread()
+
+		origns, err := netns.Get()
+		require.NoError(t, err)
+		defer origns.Close()
+		defer netns.Set(origns)
+
+		newns, err := netns.New()
+		require.NoError(t, err)
+		defer newns.Close()
+
+		f(t, newns)
+	})
+}

dialer_test.go

@@ -1,39 +0,0 @@
-package multinet
-
-import (
-	"context"
-	"net/netip"
-	"testing"
-
-	"github.com/stretchr/testify/require"
-)
-
-func TestNoSourceIPs(t *testing.T) {
-	t.Run("noop balancer", func(t *testing.T) {
-		d, err := NewDialer(Config{
-			Subnets: []Subnet{
-				{
-					Prefix: netip.MustParsePrefix("10.11.12.0/24"),
-				},
-			},
-		})
-		require.NoError(t, err)
-		conn, err := d.DialContext(context.Background(), "tcp", "10.11.12.254:8080")
-		require.ErrorIs(t, err, errNoSuitableNodeFound)
-		require.Nil(t, conn)
-	})
-	t.Run("round robin balancer", func(t *testing.T) {
-		d, err := NewDialer(Config{
-			Subnets: []Subnet{
-				{
-					Prefix: netip.MustParsePrefix("10.11.12.0/24"),
-				},
-			},
-			Balancer: BalancerTypeRoundRobin,
-		})
-		require.NoError(t, err)
-		conn, err := d.DialContext(context.Background(), "tcp", "10.11.12.254:8080")
-		require.ErrorIs(t, err, errNoSuitableNodeFound)
-		require.Nil(t, conn)
-	})
-}

go.mod

@@ -1,10 +1,13 @@
 module git.frostfs.info/TrueCloudLab/multinet
 
-go 1.22
+go 1.20
 
 require (
-	github.com/stretchr/testify v1.9.0
+	github.com/stretchr/testify v1.8.4
-	golang.org/x/net v0.26.0
+	github.com/vishvananda/netlink v1.1.0
+	github.com/vishvananda/netns v0.0.4
+	golang.org/x/net v0.17.0
+	golang.org/x/sys v0.13.0
 )
 
 require (

go.sum

@@ -2,10 +2,18 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
-github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
-golang.org/x/net v0.26.0 h1:soB7SVo0PWrY4vPW/+ay0jKDNScG2X9wFeYlXIvJsOQ=
+github.com/vishvananda/netlink v1.1.0 h1:1iyaYNBLmP6L0220aDnYQpo1QEV4t4hJ+xEEhhJH8j0=
-golang.org/x/net v0.26.0/go.mod h1:5YKkiSynbBIh3p6iOc/vibscux0x38BZDkn8sCUPxHE=
+github.com/vishvananda/netlink v1.1.0/go.mod h1:cTgwzPIzzgDAYoQrMm0EdrjRUBkTqKYppBueQtXaqoE=
+github.com/vishvananda/netns v0.0.0-20191106174202-0a2b9b5464df/go.mod h1:JP3t17pCcGlemwknint6hfoeCVQrEMVwxRLRjXpq+BU=
+github.com/vishvananda/netns v0.0.4 h1:Oeaw1EM2JMxD51g9uhtC0D7erkIjgmj8+JZc26m1YX8=
+github.com/vishvananda/netns v0.0.4/go.mod h1:SpkAiCQRtJ6TvvxPnOSyH3BMl6unz3xZlaprSwhNNJM=
+golang.org/x/net v0.17.0 h1:pVaXccu2ozPjCXewfr1S7xza/zcXTity9cCdXQYSjIM=
+golang.org/x/net v0.17.0/go.mod h1:NxSsAGuq816PNPmqtQdLE42eU2Fs7NoRIZrHJAlaCOE=
+golang.org/x/sys v0.0.0-20190606203320-7fc4e5ec1444/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
+golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

health.go

@@ -0,0 +1,73 @@
+package multinet
+
+import (
+	"net/netip"
+	"sync"
+
+	"github.com/vishvananda/netlink"
+	"github.com/vishvananda/netns"
+	"golang.org/x/sys/unix"
+)
+
+type NetlinkWatcher struct {
+	d           Multidialer
+	linkUpdates chan netlink.LinkUpdate
+	addrUpdates chan netlink.AddrUpdate
+	done        chan struct{}
+	wg          sync.WaitGroup
+}
+
+func NewNetlinkWatcher(d Multidialer) *NetlinkWatcher {
+	return &NetlinkWatcher{
+		d:           d,
+		addrUpdates: make(chan netlink.AddrUpdate, 1),
+		linkUpdates: make(chan netlink.LinkUpdate, 1),
+		done:        make(chan struct{}),
+	}
+}
+
+func (w *NetlinkWatcher) Start() error {
+	ns, err := netns.Get()
+	if err != nil {
+		return err
+	}
+
+	if err := netlink.LinkSubscribe(w.linkUpdates, w.done); err != nil {
+		return err
+	}
+	if err := netlink.AddrSubscribe(w.addrUpdates, w.done); err != nil {
+		close(w.done)
+		return err
+	}
+
+	w.wg.Add(1)
+	go w.watch(ns)
+	return nil
+}
+
+func (w *NetlinkWatcher) watch(ns netns.NsHandle) {
+	defer w.wg.Done()
+
+	for {
+		select {
+		case <-w.done:
+			return
+		case update := <-w.addrUpdates:
+			// Wont work if an multiple interfaces share IP address.
+			// Should not happen in practice.
+			ip, ok := netip.AddrFromSlice(update.LinkAddress.IP)
+			if !ok {
+				continue
+			}
+			w.d.UpdateInterface("", ip, update.NewAddr)
+		case update := <-w.linkUpdates:
+			up := update.Flags&unix.IFF_UP != 0
+			w.d.UpdateInterface(update.Link.Attrs().Name, netip.Addr{}, up)
+		}
+	}
+}
+
+func (w *NetlinkWatcher) Stop() {
+	close(w.done)
+	w.wg.Wait()
+}

health_integration_test.go

@@ -0,0 +1,157 @@
+//go:build integration
+
+package multinet
+
+import (
+	"context"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"github.com/vishvananda/netlink"
+	"github.com/vishvananda/netns"
+)
+
+func Test_NetlinkWatcher(t *testing.T) {
+	runInNewNamespace(t, "noop balancer, disable interface", func(t *testing.T, ns netns.NsHandle) {
+		setup(t, map[string][]string{
+			"testdev1": {"1.2.30.11/23"},
+			"testdev2": {"1.2.30.12/23"},
+		})
+
+		addr1 := &net.TCPAddr{IP: net.IP{1, 2, 30, 11}}
+		addr2 := &net.TCPAddr{IP: net.IP{1, 2, 30, 12}}
+
+		result := make(chan net.Addr, 1)
+		d, err := NewDialer(Config{
+			Subnets: []string{"1.2.30.0/23"},
+			DialContext: func(d *net.Dialer, _ context.Context, _, _ string) (net.Conn, error) {
+				result <- d.LocalAddr
+				return nil, nil
+			},
+		})
+		require.NoError(t, err)
+
+		w := NewNetlinkWatcher(d)
+		require.NoError(t, w.Start())
+		t.Cleanup(w.Stop)
+
+		checkDialAddr(t, d, result, addr1)
+		checkDialAddr(t, d, result, addr1)
+
+		link, err := netlink.LinkByName("testdev1")
+		require.NoError(t, err)
+		require.NoError(t, netlink.LinkSetDown(link))
+		time.Sleep(time.Second)
+
+		checkDialAddr(t, d, result, addr2)
+		checkDialAddr(t, d, result, addr2)
+
+		require.NoError(t, netlink.LinkSetUp(link))
+		time.Sleep(time.Second)
+
+		checkDialAddr(t, d, result, addr1)
+	})
+
+	runInNewNamespace(t, "noop balancer, remove address", func(t *testing.T, ns netns.NsHandle) {
+		setup(t, map[string][]string{
+			"testdev1": {"1.2.30.11/23"},
+			"testdev2": {"1.2.30.12/23"},
+		})
+
+		addr1 := &net.TCPAddr{IP: net.IP{1, 2, 30, 11}}
+		addr2 := &net.TCPAddr{IP: net.IP{1, 2, 30, 12}}
+
+		result := make(chan net.Addr, 1)
+		d, err := NewDialer(Config{
+			Subnets: []string{"1.2.30.0/23"},
+			DialContext: func(d *net.Dialer, _ context.Context, _, _ string) (net.Conn, error) {
+				result <- d.LocalAddr
+				return nil, nil
+			},
+		})
+		require.NoError(t, err)
+
+		w := NewNetlinkWatcher(d)
+		require.NoError(t, w.Start())
+		t.Cleanup(w.Stop)
+
+		checkDialAddr(t, d, result, addr1)
+		checkDialAddr(t, d, result, addr1)
+
+		link, err := netlink.LinkByName("testdev1")
+		require.NoError(t, err)
+
+		ip, err := netlink.ParseIPNet("1.2.30.11/23")
+		require.NoError(t, err)
+		require.NoError(t, netlink.AddrDel(link, &netlink.Addr{IPNet: ip}))
+		time.Sleep(time.Second)
+
+		checkDialAddr(t, d, result, addr2)
+		checkDialAddr(t, d, result, addr2)
+
+		require.NoError(t, netlink.AddrAdd(link, &netlink.Addr{IPNet: ip}))
+		time.Sleep(time.Second)
+
+		checkDialAddr(t, d, result, addr1)
+	})
+
+	runInNewNamespace(t, "round-robin balancer, disable interface", func(t *testing.T, ns netns.NsHandle) {
+		setup(t, map[string][]string{
+			"testdev1": {"1.2.30.11/23"},
+			"testdev2": {"1.2.30.12/23"},
+		})
+
+		addr1 := &net.TCPAddr{IP: net.IP{1, 2, 30, 11}}
+		addr2 := &net.TCPAddr{IP: net.IP{1, 2, 30, 12}}
+
+		result := make(chan net.Addr, 1)
+		d, err := NewDialer(Config{
+			Subnets:  []string{"1.2.30.0/23"},
+			Balancer: BalancerTypeRoundRobin,
+			DialContext: func(d *net.Dialer, _ context.Context, _, _ string) (net.Conn, error) {
+				result <- d.LocalAddr
+				return nil, nil
+			},
+		})
+		require.NoError(t, err)
+
+		w := NewNetlinkWatcher(d)
+		require.NoError(t, w.Start())
+		t.Cleanup(w.Stop)
+
+		checkDialAddr(t, d, result, addr2)
+		checkDialAddr(t, d, result, addr1)
+		checkDialAddr(t, d, result, addr2)
+
+		link, err := netlink.LinkByName("testdev1")
+		require.NoError(t, err)
+		require.NoError(t, netlink.LinkSetDown(link))
+		time.Sleep(time.Second)
+
+		checkDialAddr(t, d, result, addr2)
+		checkDialAddr(t, d, result, addr2)
+
+		require.NoError(t, netlink.LinkSetUp(link))
+		time.Sleep(time.Second)
+
+		checkDialAddr(t, d, result, addr1)
+		checkDialAddr(t, d, result, addr2)
+	})
+}
+
+func checkDialAddr(t *testing.T, d Multidialer, ch chan net.Addr, expected net.Addr) {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+
+	_, err := d.DialContext(ctx, "tcp", "1.2.30.42:12345")
+	require.NoError(t, err)
+
+	select {
+	case addr := <-ch:
+		require.Equal(t, expected, addr)
+	default:
+		require.Fail(t, "DialContext() was not called")
+	}
+}

interface.go

@@ -0,0 +1,33 @@
+package multinet
+
+import "net"
+
+// Interface provides information about net.Interface.
+type Interface interface {
+	Name() string
+	Addrs() ([]net.Addr, error)
+}
+
+type netInterface struct {
+	iface net.Interface
+}
+
+func (i *netInterface) Name() string {
+	return i.iface.Name
+}
+
+func (i *netInterface) Addrs() ([]net.Addr, error) {
+	return i.iface.Addrs()
+}
+
+func systemInterfaces() ([]Interface, error) {
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		return nil, err
+	}
+	var result []Interface
+	for _, iface := range ifaces {
+		result = append(result, &netInterface{iface: iface})
+	}
+	return result, nil
+}

multinet.patch

@@ -0,0 +1,7 @@
+@@
+@@
++import "git.frostfs.info/TrueCloudLab/multinet"
+-import "net"
+
+-net.Dial(...)
++multinet.Dial(...)

testdata/patch_0.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+	"log"
+	"net"
+)
+
+const addr = "s01.frostfs.devenv:8080"
+
+func main() {
+	_, err := net.Dial(getNetwork(), addr)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func getNetwork() string {
+	return "tcp"
+}

testdata/patch_1.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"log"
+	"net"
+)
+
+func main() {
+	ip := net.IPv4(192, 168, 0, 10)
+	_, err := net.Dial("tcp", ip.String()+":8080")
+	if err != nil {
+		log.Fatal(err)
+	}
+}