From d254f3ae80d57e22737137261a649b9c48796bba Mon Sep 17 00:00:00 2001
From: soypat <graded.sp@gmail.com>
Date: Wed, 20 Aug 2025 19:25:08 -0300
Subject: [PATCH] dhcp subnet prefix fix

---
 dhcpv4/client.go       | 16 ++++++++++++++++
 internal/net.go        |  9 +++++++++
 internal/net_tinygo.go | 12 ++++++++++++
 internal/tap.go        |  3 +--
 x/xnet/stack-async.go  |  2 +-
 5 files changed, 39 insertions(+), 3 deletions(-)
 create mode 100644 internal/net.go
 create mode 100644 internal/net_tinygo.go

diff --git a/dhcpv4/client.go b/dhcpv4/client.go
index 10270ec..eb6ab5f 100644
--- a/dhcpv4/client.go
+++ b/dhcpv4/client.go
@@ -20,6 +20,7 @@ type Client struct {
 	clientID    []byte
 	hostname    []byte
 	dns         []netip.Addr
+	ntps        []netip.Addr
 
 	svIPtos    ipv4.ToS
 	tRenew     uint32
@@ -290,6 +291,13 @@ func (c *Client) setOptions(frm Frame) error {
 			for i := 0; i < len(data); i += 4 {
 				c.dns = append(c.dns, netip.AddrFrom4([4]byte(data[i:i+4])))
 			}
+		case OptNTPServersAddresses:
+			if len(c.ntps) > 0 || len(data)%4 != 0 {
+				return nil
+			}
+			for i := 0; i < len(data); i += 4 {
+				c.ntps = append(c.ntps, netip.AddrFrom4([4]byte(data[i:i+4])))
+			}
 		}
 		return nil
 	})
@@ -355,6 +363,14 @@ func (d *Client) DNSServerFirst() netip.Addr {
 	return d.dns[0]
 }
 
+func (d *Client) SubnetPrefix() netip.Prefix {
+	if !d.offer.valid {
+		return netip.Prefix{}
+	}
+	m, _ := netip.AddrFrom4(d.offer.addr).Prefix(int(d.SubnetCIDRBits()))
+	return m
+}
+
 func (d *Client) SubnetCIDRBits() uint8 {
 	if !d.subnet.valid {
 		return 0
diff --git a/internal/net.go b/internal/net.go
new file mode 100644
index 0000000..b9e0a21
--- /dev/null
+++ b/internal/net.go
@@ -0,0 +1,9 @@
+//go:build !tinygo
+
+package internal
+
+import "net"
+
+func interfaceByName(name string) (*net.Interface, error) {
+	return net.InterfaceByName(name)
+}
diff --git a/internal/net_tinygo.go b/internal/net_tinygo.go
new file mode 100644
index 0000000..124524d
--- /dev/null
+++ b/internal/net_tinygo.go
@@ -0,0 +1,12 @@
+//go:build tinygo
+
+package internal
+
+import (
+	"errors"
+	"net"
+)
+
+func interfaceByName(name string) (*net.Interface, error) {
+	return nil, errors.New("net.InterfaceByName not implemented on TinyGo")
+}
diff --git a/internal/tap.go b/internal/tap.go
index a49037f..62dd488 100644
--- a/internal/tap.go
+++ b/internal/tap.go
@@ -7,7 +7,6 @@ import (
 	"errors"
 	"fmt"
 	"math/bits"
-	"net"
 	"net/netip"
 	"os"
 	"os/exec"
@@ -205,7 +204,7 @@ type Bridge struct {
 }
 
 func NewBridge(name string) (*Bridge, error) {
-	iface, err := net.InterfaceByName(name)
+	iface, err := interfaceByName(name)
 	if err != nil {
 		return nil, err
 	}
diff --git a/x/xnet/stack-async.go b/x/xnet/stack-async.go
index 8aa95db..a520fd3 100644
--- a/x/xnet/stack-async.go
+++ b/x/xnet/stack-async.go
@@ -480,7 +480,7 @@ func (s *StackAsync) populateDHCPResults() error {
 	router := netip.AddrFrom4(router4)
 	s.dhcpResults = DHCPResults{
 		Router:        router,
-		Subnet:        netip.PrefixFrom(router, int(s.dhcp.SubnetCIDRBits())),
+		Subnet:        s.dhcp.SubnetPrefix(),
 		AssignedAddr:  netip.AddrFrom4(assigned4),
 		ServerAddr:    addr4(s.dhcp.ServerAddr()),
 		BroadcastAddr: addr4(s.dhcp.BroadcastAddr()),