chore(all): return concrete types, accept interfaces

- Remove exported interfaces unused locally
- Define interfaces to accept arguments
- Return concrete types, not interfaces

internal/firewall/enable.go

@@ -5,10 +5,6 @@ import (
 	"fmt"
 )
 
-type Enabler interface {
-	SetEnabled(ctx context.Context, enabled bool) (err error)
-}
-
 func (c *Config) SetEnabled(ctx context.Context, enabled bool) (err error) {
 	c.stateMutex.Lock()
 	defer c.stateMutex.Unlock()

internal/firewall/firewall.go

@@ -12,16 +12,6 @@ import (
 	"github.com/qdm12/golibs/command"
 )
 
-var _ Configurator = (*Config)(nil)
-
-// Configurator allows to change firewall rules and modify network routes.
-type Configurator interface {
-	Enabler
-	VPNConnectionSetter
-	PortAllower
-	OutboundSubnetsSetter
-}
-
 type Config struct { //nolint:maligned
 	runner         command.Runner
 	logger         Logger

internal/firewall/outboundsubnets.go

@@ -8,10 +8,6 @@ import (
 	"github.com/qdm12/gluetun/internal/subnet"
 )
 
-type OutboundSubnetsSetter interface {
-	SetOutboundSubnets(ctx context.Context, subnets []net.IPNet) (err error)
-}
-
 func (c *Config) SetOutboundSubnets(ctx context.Context, subnets []net.IPNet) (err error) {
 	c.stateMutex.Lock()
 	defer c.stateMutex.Unlock()

internal/firewall/ports.go

@@ -6,11 +6,6 @@ import (
 	"strconv"
 )
 
-type PortAllower interface {
-	SetAllowedPort(ctx context.Context, port uint16, intf string) (err error)
-	RemoveAllowedPort(ctx context.Context, port uint16) (err error)
-}
-
 func (c *Config) SetAllowedPort(ctx context.Context, port uint16, intf string) (err error) {
 	c.stateMutex.Lock()
 	defer c.stateMutex.Unlock()

internal/firewall/vpn.go

@@ -7,11 +7,6 @@ import (
 	"github.com/qdm12/gluetun/internal/models"
 )
 
-type VPNConnectionSetter interface {
-	SetVPNConnection(ctx context.Context,
-		connection models.Connection, vpnIntf string) error
-}
-
 func (c *Config) SetVPNConnection(ctx context.Context,
 	connection models.Connection, vpnIntf string) (err error) {
 	c.stateMutex.Lock()