From 1f1334c6d3c15129bc14ae58dd18b8fcdc6a7454 Mon Sep 17 00:00:00 2001
From: Sergey Fedorov <vital.had@gmail.com>
Date: Wed, 29 Jan 2025 14:18:13 +0800
Subject: [PATCH] Restore support for VPN on Apple

---
 llarp/vpn/apple.hpp    | 173 +++++++++++++++++++++++++++++++++++++++++
 llarp/vpn/platform.cpp |   5 +-
 2 files changed, 177 insertions(+), 1 deletion(-)
 create mode 100644 llarp/vpn/apple.hpp

diff --git llarp/vpn/apple.hpp llarp/vpn/apple.hpp
new file mode 100644
index 000000000..f20c50ce3
--- /dev/null
+++ llarp/vpn/apple.hpp
@@ -0,0 +1,173 @@
+#pragma once
+
+#include <llarp/ev/vpn.hpp>
+#include "common.hpp"
+
+#include <sys/kern_control.h>
+#include <sys/sys_domain.h>
+#include <sys/kern_event.h>
+
+#include <sys/types.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/param.h>
+#include <sys/uio.h>
+
+#include <arpa/inet.h>
+#include <net/if.h>
+#include <net/if_var.h>
+#include <net/if_types.h>
+#include <net/route.h>
+#include <netinet/if_ether.h>
+#include <netinet/in.h>
+
+#include <fcntl.h>
+#include <ifaddrs.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+
+namespace llarp::vpn
+{
+  class AppleInterface : public NetworkInterface
+  {
+    const int m_FD;
+    const InterfaceInfo m_Info;
+    std::string m_IfName;
+
+    static void
+    Exec(std::string cmd)
+    {
+      LogDebug(cmd);
+      system(cmd.c_str());
+    }
+
+   public:
+    AppleInterface(InterfaceInfo info)
+        : m_FD{::socket(PF_SYSTEM, SOCK_DGRAM, SYSPROTO_CONTROL)}, m_Info{std::move(info)}
+    {
+      if (m_FD == -1)
+        throw std::invalid_argument{"cannot open control socket: " + std::string{strerror(errno)}};
+
+      ctl_info cinfo{};
+      const std::string apple_utun = "com.apple.net.utun_control";
+      std::copy_n(apple_utun.c_str(), apple_utun.size(), cinfo.ctl_name);
+      if (::ioctl(m_FD, CTLIOCGINFO, &cinfo) < 0)
+      {
+        ::close(m_FD);
+        throw std::runtime_error{"ioctl CTLIOCGINFO call failed: " + std::string{strerror(errno)}};
+      }
+      sockaddr_ctl addr{};
+      addr.sc_id = cinfo.ctl_id;
+
+      addr.sc_len = sizeof(addr);
+      addr.sc_family = AF_SYSTEM;
+      addr.ss_sysaddr = AF_SYS_CONTROL;
+      addr.sc_unit = 0;
+
+      if (connect(m_FD, (sockaddr*)&addr, sizeof(addr)) < 0)
+      {
+        ::close(m_FD);
+        throw std::runtime_error{
+            "cannot connect to control socket address: " + std::string{strerror(errno)}};
+      }
+      uint32_t namesz = IFNAMSIZ;
+      char name[IFNAMSIZ + 1]{};
+      if (getsockopt(m_FD, SYSPROTO_CONTROL, 2, name, &namesz) < 0)
+      {
+        ::close(m_FD);
+        throw std::runtime_error{
+            "cannot query for interface name: " + std::string{strerror(errno)}};
+      }
+      m_IfName = name;
+      for (const auto& ifaddr : m_Info.addrs)
+      {
+        if (ifaddr.fam == AF_INET)
+        {
+          const huint32_t addr = net::TruncateV6(ifaddr.range.addr);
+          const huint32_t netmask = net::TruncateV6(ifaddr.range.netmask_bits);
+          const huint32_t daddr = addr & netmask;
+          Exec(
+              "/sbin/ifconfig " + m_IfName + " " + addr.ToString() + " " + daddr.ToString()
+              + " mtu 1500 netmask 255.255.255.255 up");
+          Exec(
+              "/sbin/route add " + daddr.ToString() + " -netmask " + netmask.ToString()
+              + " -interface " + m_IfName);
+          Exec("/sbin/route add " + addr.ToString() + " -interface lo0");
+        }
+        else if (ifaddr.fam == AF_INET6)
+        {
+          Exec("/sbin/ifconfig " + m_IfName + " inet6 " + ifaddr.range.ToString());
+        }
+      }
+    }
+
+    ~AppleInterface()
+    {
+      ::close(m_FD);
+    }
+
+    std::string
+    IfName() const override
+    {
+      return m_IfName;
+    }
+
+    int
+    PollFD() const override
+    {
+      return m_FD;
+    }
+
+    net::IPPacket
+    ReadNextPacket() override
+    {
+      constexpr int uintsize = sizeof(unsigned int);
+      net::IPPacket pkt{};
+      unsigned int pktinfo = 0;
+      const struct iovec vecs[2] = {
+          {.iov_base = &pktinfo, .iov_len = uintsize},
+          {.iov_base = pkt.buf, .iov_len = sizeof(pkt.buf)}};
+      int sz = readv(m_FD, vecs, 2);
+      if (sz >= uintsize)
+        pkt.sz = sz - uintsize;
+      else if (sz >= 0 || errno == EAGAIN || errno == EWOULDBLOCK)
+        pkt.sz = 0;
+      else
+        throw std::error_code{errno, std::system_category()};
+      return pkt;
+    }
+
+    bool
+    WritePacket(net::IPPacket pkt) override
+    {
+      static unsigned int af4 = htonl(AF_INET);
+      static unsigned int af6 = htonl(AF_INET6);
+
+      const struct iovec vecs[2] = {
+          {.iov_base = pkt.IsV6() ? &af6 : &af4, .iov_len = sizeof(unsigned int)},
+          {.iov_base = pkt.buf, .iov_len = pkt.sz}};
+
+      ssize_t n = writev(m_FD, vecs, 2);
+      if (n >= (int)sizeof(unsigned int))
+      {
+        n -= sizeof(unsigned int);
+        return static_cast<size_t>(n) == pkt.sz;
+      }
+      return false;
+    }
+  };
+
+  class ApplePlatform : public Platform
+  {
+   public:
+    std::shared_ptr<NetworkInterface>
+    ObtainInterface(InterfaceInfo info) override
+    {
+      return std::make_shared<AppleInterface>(std::move(info));
+    }
+  };
+}  // namespace llarp::vpn
diff --git llarp/vpn/platform.cpp llarp/vpn/platform.cpp
index 757894b61..43e0a347b 100644
--- llarp/vpn/platform.cpp
+++ llarp/vpn/platform.cpp
@@ -11,6 +11,9 @@
 #include "linux.hpp"
 #endif
 #endif
+#ifdef __APPLE__
+#include "apple.hpp"
+#endif
 
 #include <exception>
 
@@ -38,7 +41,7 @@ namespace llarp::vpn
 #endif
 #endif
 #ifdef __APPLE__
-    throw std::runtime_error{"not supported"};
+    plat = std::make_shared<vpn::ApplePlatform>();
 #endif
     return plat;
   }