arc: Move platform2/arc/network/ to platform2/patchpanel

Next step in the arc-networkd -> patchpanel rename, this patch moves the
location of the code.

BUG=b:151879931
TEST=units,flashed image to atlas
TEST=tasts arc.PlayStore, crostini.LaunchTerminal.download

Change-Id: I1b5cf8d670e1631d46f6449b725395157bf88dde
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2115863
Tested-by: Garrick Evans <garrick@chromium.org>
Commit-Queue: Garrick Evans <garrick@chromium.org>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Eric Caruso <ejcaruso@chromium.org>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-by: Hugo Benichi <hugobenichi@google.com>
diff --git a/patchpanel/ndproxy.cc b/patchpanel/ndproxy.cc
new file mode 100644
index 0000000..4f7b051
--- /dev/null
+++ b/patchpanel/ndproxy.cc
@@ -0,0 +1,642 @@
+// Copyright 2019 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "patchpanel/ndproxy.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+#include <arpa/inet.h>
+#include <linux/filter.h>
+#include <linux/if_packet.h>
+#include <linux/in6.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <net/ethernet.h>
+#include <net/if.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+
+#include <string>
+#include <utility>
+
+#include <base/bind.h>
+
+#include "patchpanel/minijailed_process_runner.h"
+#include "patchpanel/net_util.h"
+
+namespace patchpanel {
+namespace {
+const unsigned char kBroadcastMacAddress[] = {0xff, 0xff, 0xff,
+                                              0xff, 0xff, 0xff};
+
+sock_filter kNDFrameBpfInstructions[] = {
+    // Load ethernet type.
+    BPF_STMT(BPF_LD | BPF_H | BPF_ABS, offsetof(ether_header, ether_type)),
+    // Check if it equals IPv6, if not, then goto return 0.
+    BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ETHERTYPE_IPV6, 0, 9),
+    // Move index to start of IPv6 header.
+    BPF_STMT(BPF_LDX | BPF_IMM, sizeof(ether_header)),
+    // Load IPv6 next header.
+    BPF_STMT(BPF_LD | BPF_B | BPF_IND, offsetof(ip6_hdr, ip6_nxt)),
+    // Check if equals ICMPv6, if not, then goto return 0.
+    BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 6),
+    // Move index to start of ICMPv6 header.
+    BPF_STMT(BPF_LDX | BPF_IMM, sizeof(ether_header) + sizeof(ip6_hdr)),
+    // Load ICMPv6 type.
+    BPF_STMT(BPF_LD | BPF_B | BPF_IND, offsetof(icmp6_hdr, icmp6_type)),
+    // Check if is ND ICMPv6 message.
+    BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_ROUTER_SOLICIT, 4, 0),
+    BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_ROUTER_ADVERT, 3, 0),
+    BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_NEIGHBOR_SOLICIT, 2, 0),
+    BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_NEIGHBOR_ADVERT, 1, 0),
+    // Return 0.
+    BPF_STMT(BPF_RET | BPF_K, 0),
+    // Return MAX.
+    BPF_STMT(BPF_RET | BPF_K, IP_MAXPACKET),
+};
+const sock_fprog kNDFrameBpfProgram = {
+    .len = sizeof(kNDFrameBpfInstructions) / sizeof(sock_filter),
+    .filter = kNDFrameBpfInstructions};
+
+}  // namespace
+
+constexpr ssize_t NDProxy::kTranslateErrorNotICMPv6Frame;
+constexpr ssize_t NDProxy::kTranslateErrorNotNDFrame;
+constexpr ssize_t NDProxy::kTranslateErrorInsufficientLength;
+constexpr ssize_t NDProxy::kTranslateErrorBufferMisaligned;
+
+NDProxy::NDProxy()
+    : in_frame_buffer_(AlignFrameBuffer(in_frame_buffer_extended_)),
+      out_frame_buffer_(AlignFrameBuffer(out_frame_buffer_extended_)) {}
+
+base::ScopedFD NDProxy::PreparePacketSocket() {
+  base::ScopedFD fd(
+      socket(AF_PACKET, SOCK_RAW | SOCK_CLOEXEC, htons(ETH_P_IPV6)));
+  if (!fd.is_valid()) {
+    PLOG(ERROR) << "socket() failed";
+    return base::ScopedFD();
+  }
+  if (setsockopt(fd.get(), SOL_SOCKET, SO_ATTACH_FILTER, &kNDFrameBpfProgram,
+                 sizeof(kNDFrameBpfProgram))) {
+    PLOG(ERROR) << "setsockopt(SO_ATTACH_FILTER) failed";
+    return base::ScopedFD();
+  }
+  return fd;
+}
+
+bool NDProxy::Init() {
+  rtnl_fd_ = base::ScopedFD(
+      socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE));
+  if (!rtnl_fd_.is_valid()) {
+    PLOG(ERROR) << "socket() failed for rtnetlink socket";
+    return false;
+  }
+  sockaddr_nl local = {
+      .nl_family = AF_NETLINK,
+      .nl_groups = 0,
+  };
+  if (bind(rtnl_fd_.get(), reinterpret_cast<sockaddr*>(&local), sizeof(local)) <
+      0) {
+    PLOG(ERROR) << "bind() failed on rtnetlink socket";
+    return false;
+  }
+
+  dummy_fd_ = base::ScopedFD(socket(AF_INET6, SOCK_DGRAM, 0));
+  if (!dummy_fd_.is_valid()) {
+    PLOG(ERROR) << "socket() failed for dummy socket";
+    return false;
+  }
+  return true;
+}
+
+// In an ICMPv6 Ethernet Frame *frame with length frame_len, replace the mac
+// address in option opt_type into *target_mac. nd_hdr_len indicates the length
+// of ICMPv6 ND message headers (so the first option starts after nd_hdr_len.)
+void NDProxy::ReplaceMacInIcmpOption(uint8_t* frame,
+                                     ssize_t frame_len,
+                                     size_t nd_hdr_len,
+                                     uint8_t opt_type,
+                                     const MacAddress& target_mac) {
+  nd_opt_hdr* opt;
+  nd_opt_hdr* end = reinterpret_cast<nd_opt_hdr*>(&frame[frame_len]);
+  for (opt = reinterpret_cast<nd_opt_hdr*>(frame + ETHER_HDR_LEN +
+                                           sizeof(ip6_hdr) + nd_hdr_len);
+       opt < end && opt->nd_opt_len > 0;
+       opt = reinterpret_cast<nd_opt_hdr*>(reinterpret_cast<uint64_t*>(opt) +
+                                           opt->nd_opt_len)) {
+    if (opt->nd_opt_type == opt_type) {
+      uint8_t* mac_in_opt =
+          reinterpret_cast<uint8_t*>(opt) + sizeof(nd_opt_hdr);
+      memcpy(mac_in_opt, target_mac.data(), ETHER_ADDR_LEN);
+    }
+  }
+}
+
+// RFC 4389
+// Read the input ICMPv6 frame and determine whether it should be proxied. If
+// so, fill out_frame buffer with proxied frame and return the length of proxied
+// frame (usually same with input frame length). Return a negative value if
+// proxy is not needed or error occured.
+// in_frame: buffer containing input ethernet frame; needs special alignment
+//           so that IP header is 4-bytes aligned;
+// frame_len: the length of input frame;
+// local_mac_addr: MAC address of interface that will be used to send frame;
+// out_frame: buffer for output frame; should have at least space of frame_len;
+//            needs special alignment so that IP header is 4-bytes aligned.
+ssize_t NDProxy::TranslateNDFrame(const uint8_t* in_frame,
+                                  ssize_t frame_len,
+                                  const MacAddress& local_mac_addr,
+                                  uint8_t* out_frame) {
+  if ((reinterpret_cast<uintptr_t>(in_frame + ETHER_HDR_LEN) & 0x3) != 0 ||
+      (reinterpret_cast<uintptr_t>(out_frame + ETHER_HDR_LEN) & 0x3) != 0) {
+    return kTranslateErrorBufferMisaligned;
+  }
+  if (frame_len < ETHER_HDR_LEN + sizeof(ip6_hdr) + sizeof(icmp6_hdr)) {
+    return kTranslateErrorInsufficientLength;
+  }
+  if (reinterpret_cast<const ethhdr*>(in_frame)->h_proto != htons(ETH_P_IPV6) ||
+      reinterpret_cast<const ip6_hdr*>(in_frame + ETHER_HDR_LEN)->ip6_nxt !=
+          IPPROTO_ICMPV6) {
+    return kTranslateErrorNotICMPv6Frame;
+  }
+
+  memcpy(out_frame, in_frame, frame_len);
+  ethhdr* eth = reinterpret_cast<ethhdr*>(out_frame);
+  ip6_hdr* ip6 = reinterpret_cast<ip6_hdr*>(out_frame + ETHER_HDR_LEN);
+  icmp6_hdr* icmp6 =
+      reinterpret_cast<icmp6_hdr*>(out_frame + ETHER_HDR_LEN + sizeof(ip6_hdr));
+
+  // If destination MAC is unicast (Individual/Group bit in MAC address == 0),
+  // it needs to be modified so guest OS L3 stack can see it.
+  // For proxy cascading case, we also need to recheck if destination MAC is
+  // ff:ff:ff:ff:ff:ff (which must have been filled by an upstream proxy).
+  if (!(eth->h_dest[0] & 0x1) ||
+      memcmp(eth->h_dest, kBroadcastMacAddress, ETHER_ADDR_LEN) == 0) {
+    MacAddress neighbor_mac;
+    if (GetNeighborMac(ip6->ip6_dst, &neighbor_mac)) {
+      memcpy(eth->h_dest, neighbor_mac.data(), ETHER_ADDR_LEN);
+    } else {
+      // If we can't resolve the destination IP into MAC from kernel neighbor
+      // table, fill destination MAC with broadcast MAC instead.
+      memcpy(eth->h_dest, kBroadcastMacAddress, ETHER_ADDR_LEN);
+    }
+  }
+
+  switch (icmp6->icmp6_type) {
+    case ND_ROUTER_SOLICIT:
+      ReplaceMacInIcmpOption(out_frame, frame_len, sizeof(nd_router_solicit),
+                             ND_OPT_SOURCE_LINKADDR, local_mac_addr);
+      break;
+    case ND_ROUTER_ADVERT: {
+      // RFC 4389 Section 4.1.3.3 - Set Proxy bit
+      nd_router_advert* ra = reinterpret_cast<nd_router_advert*>(icmp6);
+      if (ra->nd_ra_flags_reserved & 0x04) {
+        // According to RFC 4389, an RA packet with 'Proxy' bit set already
+        // should not be proxied again, in order to avoid loop. However, we'll
+        // need this form of proxy cascading in Crostini (Host->VM->Container)
+        // so we are ignoring the check here. Note that we know we are doing RA
+        // proxy in only one direction so there should be no loop.
+      }
+      ra->nd_ra_flags_reserved |= 0x04;
+
+      ReplaceMacInIcmpOption(out_frame, frame_len, sizeof(nd_router_advert),
+                             ND_OPT_SOURCE_LINKADDR, local_mac_addr);
+      break;
+    }
+    case ND_NEIGHBOR_SOLICIT:
+      ReplaceMacInIcmpOption(out_frame, frame_len, sizeof(nd_neighbor_solicit),
+                             ND_OPT_SOURCE_LINKADDR, local_mac_addr);
+      break;
+    case ND_NEIGHBOR_ADVERT:
+      ReplaceMacInIcmpOption(out_frame, frame_len, sizeof(nd_neighbor_advert),
+                             ND_OPT_TARGET_LINKADDR, local_mac_addr);
+      break;
+    default:
+      return kTranslateErrorNotNDFrame;
+  }
+
+  // We need to clear the old checksum first so checksum calculation does not
+  // wrongly take old checksum into account.
+  icmp6->icmp6_cksum = 0;
+  icmp6->icmp6_cksum = Icmpv6Checksum(ip6, icmp6);
+
+  memcpy(eth->h_source, local_mac_addr.data(), ETHER_ADDR_LEN);
+  return frame_len;
+}
+
+void NDProxy::ReadAndProcessOneFrame(int fd) {
+  sockaddr_ll dst_addr;
+  struct iovec iov = {
+      .iov_base = in_frame_buffer_,
+      .iov_len = IP_MAXPACKET,
+  };
+  msghdr hdr = {
+      .msg_name = &dst_addr,
+      .msg_namelen = sizeof(dst_addr),
+      .msg_iov = &iov,
+      .msg_iovlen = 1,
+      .msg_control = nullptr,
+      .msg_controllen = 0,
+      .msg_flags = 0,
+  };
+
+  ssize_t len;
+  if ((len = recvmsg(fd, &hdr, 0)) < 0) {
+    PLOG(ERROR) << "recvmsg() failed";
+    return;
+  }
+  ip6_hdr* ip6 = reinterpret_cast<ip6_hdr*>(in_frame_buffer_ + ETH_HLEN);
+  icmp6_hdr* icmp6 = reinterpret_cast<icmp6_hdr*>(
+      in_frame_buffer_ + ETHER_HDR_LEN + sizeof(ip6_hdr));
+
+  if (ip6->ip6_nxt != IPPROTO_ICMPV6 || icmp6->icmp6_type < ND_ROUTER_SOLICIT ||
+      icmp6->icmp6_type > ND_NEIGHBOR_ADVERT)
+    return;
+
+  // Notify DeviceManager on receiving NA from guest, so a /128 route to the
+  // guest can be added on the host.
+  if (icmp6->icmp6_type == ND_NEIGHBOR_ADVERT &&
+      IsGuestInterface(dst_addr.sll_ifindex) &&
+      !guest_discovery_handler_.is_null()) {
+    nd_neighbor_advert* na = reinterpret_cast<nd_neighbor_advert*>(icmp6);
+    if (((na->nd_na_target.s6_addr[0] & 0xe0) == 0x20)        // Global Unicast
+        || ((na->nd_na_target.s6_addr[0] & 0xfe) == 0xfc)) {  // Unique Local
+      char ifname[IFNAMSIZ];
+      if_indextoname(dst_addr.sll_ifindex, ifname);
+      char ipv6_addr_str[INET6_ADDRSTRLEN];
+      inet_ntop(AF_INET6, &(na->nd_na_target.s6_addr), ipv6_addr_str,
+                INET6_ADDRSTRLEN);
+      guest_discovery_handler_.Run(std::string(ifname),
+                                   std::string(ipv6_addr_str));
+    }
+  }
+
+  auto map_entry = MapForType(icmp6->icmp6_type)->find(dst_addr.sll_ifindex);
+  if (map_entry == MapForType(icmp6->icmp6_type)->end())
+    return;
+  const auto& target_ifs = map_entry->second;
+  for (int target_if : target_ifs) {
+    MacAddress local_mac;
+    if (!GetLocalMac(target_if, &local_mac))
+      continue;
+    int result =
+        TranslateNDFrame(in_frame_buffer_, len, local_mac, out_frame_buffer_);
+    if (result < 0) {
+      switch (result) {
+        case kTranslateErrorNotICMPv6Frame:
+          LOG(DFATAL) << "Attempt to TranslateNDFrame on a non-ICMPv6 frame";
+          return;
+        case kTranslateErrorNotNDFrame:
+          LOG(DFATAL) << "Attempt to TranslateNDFrame on a non-NDP frame, "
+                         "icmpv6 type = "
+                      << static_cast<int>(reinterpret_cast<icmp6_hdr*>(
+                                              in_frame_buffer_ + ETHER_HDR_LEN +
+                                              sizeof(ip6_hdr))
+                                              ->icmp6_type);
+          return;
+        case kTranslateErrorInsufficientLength:
+          LOG(DFATAL) << "TranslateNDFrame failed: frame_len = " << len
+                      << " is too small";
+          return;
+        default:
+          LOG(DFATAL) << "Unknown error in TranslateNDFrame";
+          return;
+      }
+    }
+
+    struct iovec iov_out = {
+        .iov_base = out_frame_buffer_,
+        .iov_len = static_cast<size_t>(len),
+    };
+    sockaddr_ll addr = {
+        .sll_family = AF_PACKET,
+        .sll_protocol = htons(ETH_P_IPV6),
+        .sll_ifindex = target_if,
+        .sll_halen = ETHER_ADDR_LEN,
+    };
+    memcpy(addr.sll_addr, reinterpret_cast<ethhdr*>(out_frame_buffer_)->h_dest,
+           ETHER_ADDR_LEN);
+    msghdr hdr = {
+        .msg_name = &addr,
+        .msg_namelen = sizeof(addr),
+        .msg_iov = &iov_out,
+        .msg_iovlen = 1,
+        .msg_control = nullptr,
+        .msg_controllen = 0,
+    };
+    if (sendmsg(fd, &hdr, 0) < 0) {
+      PLOG(ERROR) << "sendmsg() failed on interface " << target_if;
+    }
+  }
+}
+
+bool NDProxy::GetLocalMac(int if_id, MacAddress* mac_addr) {
+  ifreq ifr = {
+      .ifr_ifindex = if_id,
+  };
+  if (ioctl(dummy_fd_.get(), SIOCGIFNAME, &ifr) < 0) {
+    PLOG(ERROR) << "ioctl() failed to get interface name on interface "
+                << if_id;
+    return false;
+  }
+  if (ioctl(dummy_fd_.get(), SIOCGIFHWADDR, &ifr) < 0) {
+    PLOG(ERROR) << "ioctl() failed to get MAC address on interface " << if_id;
+    return false;
+  }
+  memcpy(mac_addr->data(), ifr.ifr_addr.sa_data, ETHER_ADDR_LEN);
+  return true;
+}
+
+bool NDProxy::GetNeighborMac(const in6_addr& ipv6_addr, MacAddress* mac_addr) {
+  sockaddr_nl kernel = {
+      .nl_family = AF_NETLINK,
+      .nl_groups = 0,
+  };
+  struct nl_req {
+    nlmsghdr hdr;
+    rtgenmsg gen;
+  } req = {
+      .hdr =
+          {
+              .nlmsg_len = NLMSG_LENGTH(sizeof(rtgenmsg)),
+              .nlmsg_type = RTM_GETNEIGH,
+              .nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP,
+              .nlmsg_seq = 1,
+          },
+      .gen =
+          {
+              .rtgen_family = AF_INET6,
+          },
+  };
+  iovec io_req = {
+      .iov_base = &req,
+      .iov_len = req.hdr.nlmsg_len,
+  };
+  msghdr rtnl_req = {
+      .msg_name = &kernel,
+      .msg_namelen = sizeof(kernel),
+      .msg_iov = &io_req,
+      .msg_iovlen = 1,
+  };
+  if (sendmsg(rtnl_fd_.get(), &rtnl_req, 0) < 0) {
+    PLOG(ERROR) << "sendmsg() failed on rtnetlink socket";
+    return false;
+  }
+
+  static constexpr size_t kRtnlReplyBufferSize = 32768;
+  char reply_buffer[kRtnlReplyBufferSize];
+  iovec io_reply = {
+      .iov_base = reply_buffer,
+      .iov_len = kRtnlReplyBufferSize,
+  };
+  msghdr rtnl_reply = {
+      .msg_name = &kernel,
+      .msg_namelen = sizeof(kernel),
+      .msg_iov = &io_reply,
+      .msg_iovlen = 1,
+  };
+
+  bool any_entry_matched = false;
+  bool done = false;
+  while (!done) {
+    ssize_t len;
+    if ((len = recvmsg(rtnl_fd_.get(), &rtnl_reply, 0)) < 0) {
+      PLOG(ERROR) << "recvmsg() failed on rtnetlink socket";
+      return false;
+    }
+    for (nlmsghdr* msg_ptr = reinterpret_cast<nlmsghdr*>(reply_buffer);
+         NLMSG_OK(msg_ptr, len); msg_ptr = NLMSG_NEXT(msg_ptr, len)) {
+      switch (msg_ptr->nlmsg_type) {
+        case NLMSG_DONE: {
+          done = true;
+          break;
+        }
+        case RTM_NEWNEIGH: {
+          // Bitmap - 0x1: Found IP match; 0x2: found MAC address;
+          uint8_t current_entry_status = 0x0;
+          uint8_t current_mac[ETHER_ADDR_LEN];
+          ndmsg* nd_msg = reinterpret_cast<ndmsg*>(NLMSG_DATA(msg_ptr));
+          rtattr* rt_attr = reinterpret_cast<rtattr*>(RTM_RTA(nd_msg));
+          size_t rt_attr_len = RTM_PAYLOAD(msg_ptr);
+          for (; RTA_OK(rt_attr, rt_attr_len);
+               rt_attr = RTA_NEXT(rt_attr, rt_attr_len)) {
+            if (rt_attr->rta_type == NDA_DST &&
+                memcmp(&ipv6_addr, RTA_DATA(rt_attr), sizeof(in6_addr)) == 0) {
+              current_entry_status |= 0x1;
+            } else if (rt_attr->rta_type == NDA_LLADDR) {
+              current_entry_status |= 0x2;
+              memcpy(current_mac, RTA_DATA(rt_attr), ETHER_ADDR_LEN);
+            }
+          }
+          if (current_entry_status == 0x3) {
+            memcpy(mac_addr->data(), current_mac, ETHER_ADDR_LEN);
+            any_entry_matched = true;
+          }
+          break;
+        }
+        default: {
+          LOG(WARNING) << "received unexpected rtnetlink message type "
+                       << msg_ptr->nlmsg_type << ", length "
+                       << msg_ptr->nlmsg_len;
+          break;
+        }
+      }
+    }
+  }
+  return any_entry_matched;
+}
+
+void NDProxy::RegisterOnGuestIpDiscoveryHandler(
+    const base::Callback<void(const std::string&, const std::string&)>&
+        handler) {
+  guest_discovery_handler_ = handler;
+}
+
+NDProxy::interface_mapping* NDProxy::MapForType(uint8_t type) {
+  switch (type) {
+    case ND_ROUTER_SOLICIT:
+      return &if_map_rs_;
+    case ND_ROUTER_ADVERT:
+      return &if_map_ra_;
+    case ND_NEIGHBOR_SOLICIT:
+      return &if_map_ns_na_;
+    case ND_NEIGHBOR_ADVERT:
+      return &if_map_ns_na_;
+    default:
+      LOG(DFATAL) << "Attempt to get interface map on illegal icmpv6 type "
+                  << static_cast<int>(type);
+      return nullptr;
+  }
+}
+
+bool NDProxy::AddInterfacePair(const std::string& ifname_physical,
+                               const std::string& ifname_guest) {
+  LOG(INFO) << "Adding interface pair between physical: " << ifname_physical
+            << ", guest: " << ifname_guest;
+  int ifid_physical = if_nametoindex(ifname_physical.c_str());
+  if (ifid_physical == 0) {
+    PLOG(ERROR) << "Get interface index failed on " << ifname_physical;
+    return false;
+  }
+  int ifid_guest = if_nametoindex(ifname_guest.c_str());
+  if (ifid_guest == 0) {
+    PLOG(ERROR) << "Get interface index failed on " << ifname_guest;
+    return false;
+  }
+  if (ifid_physical == ifid_guest) {
+    LOG(ERROR) << "Rejected attempt to forward between same interface "
+               << ifname_physical << " and " << ifname_guest;
+    return false;
+  }
+  if_map_rs_[ifid_guest].insert(ifid_physical);
+  if_map_ra_[ifid_physical].insert(ifid_guest);
+  if_map_ns_na_[ifid_physical].insert(ifid_guest);
+  if_map_ns_na_[ifid_guest].insert(ifid_physical);
+  for (int ifid_other_guest : if_map_ra_[ifid_physical]) {
+    if (ifid_other_guest != ifid_guest) {
+      if_map_ns_na_[ifid_other_guest].insert(ifid_guest);
+      if_map_ns_na_[ifid_guest].insert(ifid_other_guest);
+    }
+  }
+  return true;
+}
+
+bool NDProxy::RemoveInterfacePair(const std::string& ifname_physical,
+                                  const std::string& ifname_guest) {
+  LOG(INFO) << "Removing interface pair between physical: " << ifname_physical
+            << ", guest: " << ifname_guest;
+  int ifid_physical = if_nametoindex(ifname_physical.c_str());
+  if (ifid_physical == 0) {
+    PLOG(ERROR) << "Get interface index failed on " << ifname_physical;
+    return false;
+  }
+  int ifid_guest = if_nametoindex(ifname_guest.c_str());
+  if (ifid_guest == 0) {
+    PLOG(ERROR) << "Get interface index failed on " << ifname_guest;
+    return false;
+  }
+  if (ifid_physical == ifid_guest) {
+    LOG(ERROR) << "Rejected attempt to forward between same interface "
+               << ifname_physical << " and " << ifname_guest;
+    return false;
+  }
+  if_map_rs_.erase(ifid_guest);
+  if_map_ra_[ifid_physical].erase(ifid_guest);
+  if_map_ns_na_.erase(ifid_guest);
+  if_map_ns_na_[ifid_physical].erase(ifid_guest);
+  for (int ifid_other_guest : if_map_ra_[ifid_physical]) {
+    if_map_ns_na_[ifid_other_guest].erase(ifid_guest);
+  }
+  return true;
+}
+
+bool NDProxy::RemoveInterface(const std::string& ifname) {
+  LOG(INFO) << "Removing physical interface " << ifname;
+  int ifindex = if_nametoindex(ifname.c_str());
+  if (ifindex == 0) {
+    PLOG(ERROR) << "Get interface index failed on " << ifname;
+    return false;
+  }
+  for (int ifid_guest : if_map_ra_[ifindex]) {
+    if_map_rs_.erase(ifid_guest);
+    if_map_ns_na_.erase(ifid_guest);
+  }
+  if_map_ra_.erase(ifindex);
+  if_map_ns_na_.erase(ifindex);
+  return true;
+}
+
+bool NDProxy::IsGuestInterface(int ifindex) {
+  return if_map_rs_.find(ifindex) != if_map_rs_.end();
+}
+
+NDProxyDaemon::NDProxyDaemon(base::ScopedFD control_fd)
+    : msg_dispatcher_(
+          std::make_unique<MessageDispatcher>(std::move(control_fd))) {}
+
+NDProxyDaemon::~NDProxyDaemon() {}
+
+int NDProxyDaemon::OnInit() {
+  // Prevent the main process from sending us any signals.
+  if (setsid() < 0) {
+    PLOG(ERROR) << "Failed to created a new session with setsid: exiting";
+    return EX_OSERR;
+  }
+
+  EnterChildProcessJail();
+
+  // Register control fd callbacks
+  if (msg_dispatcher_) {
+    msg_dispatcher_->RegisterFailureHandler(base::Bind(
+        &NDProxyDaemon::OnParentProcessExit, weak_factory_.GetWeakPtr()));
+    msg_dispatcher_->RegisterDeviceMessageHandler(base::Bind(
+        &NDProxyDaemon::OnDeviceMessage, weak_factory_.GetWeakPtr()));
+  }
+
+  // Initialize NDProxy and register guest IP discovery callback
+  if (!proxy_.Init()) {
+    PLOG(ERROR) << "Failed to initialize NDProxy internal state";
+    return EX_OSERR;
+  }
+  proxy_.RegisterOnGuestIpDiscoveryHandler(base::Bind(
+      &NDProxyDaemon::OnGuestIpDiscovery, weak_factory_.GetWeakPtr()));
+
+  // Initialize data fd
+  fd_ = NDProxy::PreparePacketSocket();
+  if (!fd_.is_valid()) {
+    return EX_OSERR;
+  }
+
+  // Start watching on data fd
+  watcher_ = base::FileDescriptorWatcher::WatchReadable(
+      fd_.get(), base::Bind(&NDProxyDaemon::OnDataSocketReadReady,
+                            weak_factory_.GetWeakPtr()));
+  LOG(INFO) << "Started watching on packet fd...";
+
+  return Daemon::OnInit();
+}
+
+void NDProxyDaemon::OnDataSocketReadReady() {
+  proxy_.ReadAndProcessOneFrame(fd_.get());
+}
+
+void NDProxyDaemon::OnParentProcessExit() {
+  LOG(ERROR) << "Quitting because the parent process died";
+  Quit();
+}
+
+void NDProxyDaemon::OnDeviceMessage(const DeviceMessage& msg) {
+  const std::string& dev_ifname = msg.dev_ifname();
+  LOG_IF(DFATAL, dev_ifname.empty())
+      << "Received DeviceMessage w/ empty dev_ifname";
+  if (msg.has_teardown()) {
+    if (msg.has_br_ifname()) {
+      proxy_.RemoveInterfacePair(dev_ifname, msg.br_ifname());
+    } else {
+      proxy_.RemoveInterface(dev_ifname);
+    }
+  } else if (msg.has_br_ifname()) {
+    proxy_.AddInterfacePair(dev_ifname, msg.br_ifname());
+  }
+}
+
+void NDProxyDaemon::OnGuestIpDiscovery(const std::string& ifname,
+                                       const std::string& ip6addr) {
+  // Send information back to DeviceManager
+  if (!msg_dispatcher_)
+    return;
+  DeviceMessage msg;
+  msg.set_dev_ifname(ifname);
+  msg.set_guest_ip6addr(ip6addr);
+  IpHelperMessage ipm;
+  *ipm.mutable_device_message() = msg;
+  msg_dispatcher_->SendMessage(ipm);
+}
+
+}  // namespace patchpanel