clatd_test.cpp

/*
 * Copyright 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * clatd_test.cpp - unit tests for clatd
 */

#include <iostream>

#include <arpa/inet.h>
#include <netinet/in6.h>
#include <stdio.h>
#include <sys/uio.h>

#include <gtest/gtest.h>

#include "netutils/ifc.h"
#include "tun_interface.h"

extern "C" {
#include "clatd.h"
#include "config.h"
#include "getaddr.h"
#include "netutils/checksum.h"
#include "translate.h"
}

// For convenience.
#define ARRAYSIZE(x) sizeof((x)) / sizeof((x)[0])

using android::net::TunInterface;

// Default translation parameters.
static const char kIPv4LocalAddr[]  = "192.0.0.4";
static const char kIPv6LocalAddr[]  = "2001:db8:0:b11::464";
static const char kIPv6PlatSubnet[] = "64:ff9b::";

// clang-format off
// Test packet portions. Defined as macros because it's easy to concatenate them to make packets.
#define IPV4_HEADER(p, c1, c2) \
    0x45, 0x00,    0,   41,  /* Version=4, IHL=5, ToS=0x80, len=41 */     \
    0x00, 0x00, 0x40, 0x00,  /* ID=0x0000, flags=IP_DF, offset=0 */       \
      55,  (p), (c1), (c2),  /* TTL=55, protocol=p, checksum=c1,c2 */     \
     192,    0,    0,    4,  /* Src=192.0.0.4 */                          \
       8,    8,    8,    8,  /* Dst=8.8.8.8 */
#define IPV4_UDP_HEADER IPV4_HEADER(IPPROTO_UDP, 0x73, 0xb0)
#define IPV4_ICMP_HEADER IPV4_HEADER(IPPROTO_ICMP, 0x73, 0xc0)

#define IPV6_HEADER(p) \
    0x60, 0x00,    0,    0,  /* Version=6, tclass=0x00, flowlabel=0 */    \
       0,   21,  (p),   55,  /* plen=11, nxthdr=p, hlim=55 */             \
    0x20, 0x01, 0x0d, 0xb8,  /* Src=2001:db8:0:b11::464 */                \
    0x00, 0x00, 0x0b, 0x11,                                               \
    0x00, 0x00, 0x00, 0x00,                                               \
    0x00, 0x00, 0x04, 0x64,                                               \
    0x00, 0x64, 0xff, 0x9b,  /* Dst=64:ff9b::8.8.8.8 */                   \
    0x00, 0x00, 0x00, 0x00,                                               \
    0x00, 0x00, 0x00, 0x00,                                               \
    0x08, 0x08, 0x08, 0x08,
#define IPV6_UDP_HEADER IPV6_HEADER(IPPROTO_UDP)
#define IPV6_ICMPV6_HEADER IPV6_HEADER(IPPROTO_ICMPV6)

#define UDP_LEN 21
#define UDP_HEADER \
    0xc8, 0x8b,    0,   53,  /* Port 51339->53 */                         \
    0x00, UDP_LEN, 0,    0,  /* Length 21, checksum empty for now */

#define PAYLOAD 'H', 'e', 'l', 'l', 'o', ' ', 0x4e, 0xb8, 0x96, 0xe7, 0x95, 0x8c, 0x00

#define IPV4_PING \
    0x08, 0x00, 0x88, 0xd0,  /* Type 8, code 0, checksum 0x88d0 */        \
    0xd0, 0x0d, 0x00, 0x03,  /* ID=0xd00d, seq=3 */

#define IPV6_PING \
    0x80, 0x00, 0xc3, 0x42,  /* Type 128, code 0, checksum 0xc342 */      \
    0xd0, 0x0d, 0x00, 0x03,  /* ID=0xd00d, seq=3 */

// Macros to return pseudo-headers from packets.
#define IPV4_PSEUDOHEADER(ip, tlen)                                  \
  ip[12], ip[13], ip[14], ip[15],        /* Source address      */   \
  ip[16], ip[17], ip[18], ip[19],        /* Destination address */   \
  0, ip[9],                              /* 0, protocol         */   \
  ((tlen) >> 16) & 0xff, (tlen) & 0xff,  /* Transport length */

#define IPV6_PSEUDOHEADER(ip6, protocol, tlen)                       \
  ip6[8],  ip6[9],  ip6[10], ip6[11],  /* Source address */          \
  ip6[12], ip6[13], ip6[14], ip6[15],                                \
  ip6[16], ip6[17], ip6[18], ip6[19],                                \
  ip6[20], ip6[21], ip6[22], ip6[23],                                \
  ip6[24], ip6[25], ip6[26], ip6[27],  /* Destination address */     \
  ip6[28], ip6[29], ip6[30], ip6[31],                                \
  ip6[32], ip6[33], ip6[34], ip6[35],                                \
  ip6[36], ip6[37], ip6[38], ip6[39],                                \
  ((tlen) >> 24) & 0xff,               /* Transport length */        \
  ((tlen) >> 16) & 0xff,                                             \
  ((tlen) >> 8) & 0xff,                                              \
  (tlen) & 0xff,                                                     \
  0, 0, 0, (protocol),

// A fragmented DNS request.
static const uint8_t kIPv4Frag1[] = {
    0x45, 0x00, 0x00, 0x24, 0xfe, 0x47, 0x20, 0x00, 0x40, 0x11,
    0x8c, 0x6d, 0xc0, 0x00, 0x00, 0x04, 0x08, 0x08, 0x08, 0x08,
    0x14, 0x5d, 0x00, 0x35, 0x00, 0x29, 0x68, 0xbb, 0x50, 0x47,
    0x01, 0x00, 0x00, 0x01, 0x00, 0x00
};
static const uint8_t kIPv4Frag2[] = {
    0x45, 0x00, 0x00, 0x24, 0xfe, 0x47, 0x20, 0x02, 0x40, 0x11,
    0x8c, 0x6b, 0xc0, 0x00, 0x00, 0x04, 0x08, 0x08, 0x08, 0x08,
    0x00, 0x00, 0x00, 0x00, 0x04, 0x69, 0x70, 0x76, 0x34, 0x06,
    0x67, 0x6f, 0x6f, 0x67, 0x6c, 0x65
};
static const uint8_t kIPv4Frag3[] = {
    0x45, 0x00, 0x00, 0x1d, 0xfe, 0x47, 0x00, 0x04, 0x40, 0x11,
    0xac, 0x70, 0xc0, 0x00, 0x00, 0x04, 0x08, 0x08, 0x08, 0x08,
    0x03, 0x63, 0x6f, 0x6d, 0x00, 0x00, 0x01, 0x00, 0x01
};
static const uint8_t *kIPv4Fragments[] = { kIPv4Frag1, kIPv4Frag2, kIPv4Frag3 };
static const size_t kIPv4FragLengths[] = { sizeof(kIPv4Frag1), sizeof(kIPv4Frag2),
                                           sizeof(kIPv4Frag3) };

static const uint8_t kIPv6Frag1[] = {
    0x60, 0x00, 0x00, 0x00, 0x00, 0x18, 0x2c, 0x40, 0x20, 0x01,
    0x0d, 0xb8, 0x00, 0x00, 0x0b, 0x11, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x04, 0x64, 0x00, 0x64, 0xff, 0x9b, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x08, 0x08, 0x08,
    0x11, 0x00, 0x00, 0x01, 0x00, 0x00, 0xfe, 0x47, 0x14, 0x5d,
    0x00, 0x35, 0x00, 0x29, 0xeb, 0x91, 0x50, 0x47, 0x01, 0x00,
    0x00, 0x01, 0x00, 0x00
};

static const uint8_t kIPv6Frag2[] = {
    0x60, 0x00, 0x00, 0x00, 0x00, 0x18, 0x2c, 0x40, 0x20, 0x01,
    0x0d, 0xb8, 0x00, 0x00, 0x0b, 0x11, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x04, 0x64, 0x00, 0x64, 0xff, 0x9b, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x08, 0x08, 0x08,
    0x11, 0x00, 0x00, 0x11, 0x00, 0x00, 0xfe, 0x47, 0x00, 0x00,
    0x00, 0x00, 0x04, 0x69, 0x70, 0x76, 0x34, 0x06, 0x67, 0x6f,
    0x6f, 0x67, 0x6c, 0x65
};

static const uint8_t kIPv6Frag3[] = {
    0x60, 0x00, 0x00, 0x00, 0x00, 0x11, 0x2c, 0x40, 0x20, 0x01,
    0x0d, 0xb8, 0x00, 0x00, 0x0b, 0x11, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x04, 0x64, 0x00, 0x64, 0xff, 0x9b, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x08, 0x08, 0x08,
    0x11, 0x00, 0x00, 0x20, 0x00, 0x00, 0xfe, 0x47, 0x03, 0x63,
    0x6f, 0x6d, 0x00, 0x00, 0x01, 0x00, 0x01
};
static const uint8_t *kIPv6Fragments[] = { kIPv6Frag1, kIPv6Frag2, kIPv6Frag3 };
static const size_t kIPv6FragLengths[] = { sizeof(kIPv6Frag1), sizeof(kIPv6Frag2),
                                           sizeof(kIPv6Frag3) };

static const uint8_t kReassembledIPv4[] = {
    0x45, 0x00, 0x00, 0x3d, 0xfe, 0x47, 0x00, 0x00, 0x40, 0x11,
    0xac, 0x54, 0xc0, 0x00, 0x00, 0x04, 0x08, 0x08, 0x08, 0x08,
    0x14, 0x5d, 0x00, 0x35, 0x00, 0x29, 0x68, 0xbb, 0x50, 0x47,
    0x01, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x04, 0x69, 0x70, 0x76, 0x34, 0x06, 0x67, 0x6f, 0x6f, 0x67,
    0x6c, 0x65, 0x03, 0x63, 0x6f, 0x6d, 0x00, 0x00, 0x01, 0x00,
    0x01
};
// clang-format on

// Expected checksums.
static const uint32_t kUdpPartialChecksum     = 0xd5c8;
static const uint32_t kPayloadPartialChecksum = 0x31e9c;
static const uint16_t kUdpV4Checksum          = 0xd0c7;
static const uint16_t kUdpV6Checksum          = 0xa74a;

uint8_t ip_version(const uint8_t *packet) {
  uint8_t version = packet[0] >> 4;
  return version;
}

int is_ipv4_fragment(struct iphdr *ip) {
  // A packet is a fragment if its fragment offset is nonzero or if the MF flag is set.
  return ntohs(ip->frag_off) & (IP_OFFMASK | IP_MF);
}

int is_ipv6_fragment(struct ip6_hdr *ip6, size_t len) {
  if (ip6->ip6_nxt != IPPROTO_FRAGMENT) {
    return 0;
  }
  struct ip6_frag *frag = (struct ip6_frag *)(ip6 + 1);
  return len >= sizeof(*ip6) + sizeof(*frag) &&
         (frag->ip6f_offlg & (IP6F_OFF_MASK | IP6F_MORE_FRAG));
}

int ipv4_fragment_offset(struct iphdr *ip) {
  return ntohs(ip->frag_off) & IP_OFFMASK;
}

int ipv6_fragment_offset(struct ip6_frag *frag) {
  return ntohs((frag->ip6f_offlg & IP6F_OFF_MASK) >> 3);
}

void check_packet(const uint8_t *packet, size_t len, const char *msg) {
  void *payload;
  size_t payload_length    = 0;
  uint32_t pseudo_checksum = 0;
  uint8_t protocol         = 0;
  int version              = ip_version(packet);
  switch (version) {
    case 4: {
      struct iphdr *ip = (struct iphdr *)packet;
      ASSERT_GE(len, sizeof(*ip)) << msg << ": IPv4 packet shorter than IPv4 header\n";
      EXPECT_EQ(5, ip->ihl) << msg << ": Unsupported IP header length\n";
      EXPECT_EQ(len, ntohs(ip->tot_len)) << msg << ": Incorrect IPv4 length\n";
      EXPECT_EQ(0, ip_checksum(ip, sizeof(*ip))) << msg << ": Incorrect IP checksum\n";
      protocol = ip->protocol;
      payload  = ip + 1;
      if (!is_ipv4_fragment(ip)) {
        payload_length  = len - sizeof(*ip);
        pseudo_checksum = ipv4_pseudo_header_checksum(ip, payload_length);
      }
      ASSERT_TRUE(protocol == IPPROTO_TCP || protocol == IPPROTO_UDP || protocol == IPPROTO_ICMP)
        << msg << ": Unsupported IPv4 protocol " << protocol << "\n";
      break;
    }
    case 6: {
      struct ip6_hdr *ip6 = (struct ip6_hdr *)packet;
      ASSERT_GE(len, sizeof(*ip6)) << msg << ": IPv6 packet shorter than IPv6 header\n";
      EXPECT_EQ(len - sizeof(*ip6), htons(ip6->ip6_plen)) << msg << ": Incorrect IPv6 length\n";

      if (ip6->ip6_nxt == IPPROTO_FRAGMENT) {
        struct ip6_frag *frag = (struct ip6_frag *)(ip6 + 1);
        ASSERT_GE(len, sizeof(*ip6) + sizeof(*frag))
          << msg << ": IPv6 fragment: short fragment header\n";
        protocol = frag->ip6f_nxt;
        payload  = frag + 1;
        // Even though the packet has a Fragment header, it might not be a fragment.
        if (!is_ipv6_fragment(ip6, len)) {
          payload_length = len - sizeof(*ip6) - sizeof(*frag);
        }
      } else {
        // Since there are no extension headers except Fragment, this must be the payload.
        protocol       = ip6->ip6_nxt;
        payload        = ip6 + 1;
        payload_length = len - sizeof(*ip6);
      }
      ASSERT_TRUE(protocol == IPPROTO_TCP || protocol == IPPROTO_UDP || protocol == IPPROTO_ICMPV6)
        << msg << ": Unsupported IPv6 next header " << protocol;
      if (payload_length) {
        pseudo_checksum = ipv6_pseudo_header_checksum(ip6, payload_length, protocol);
      }
      break;
    }
    default:
      FAIL() << msg << ": Unsupported IP version " << version << "\n";
      return;
  }

  // If we understand the payload, verify the checksum.
  if (payload_length) {
    uint16_t checksum;
    switch (protocol) {
      case IPPROTO_UDP:
      case IPPROTO_TCP:
      case IPPROTO_ICMPV6:
        checksum = ip_checksum_finish(ip_checksum_add(pseudo_checksum, payload, payload_length));
        break;
      case IPPROTO_ICMP:
        checksum = ip_checksum(payload, payload_length);
        break;
      default:
        checksum = 0;  // Don't check.
        break;
    }
    EXPECT_EQ(0, checksum) << msg << ": Incorrect transport checksum\n";
  }

  if (protocol == IPPROTO_UDP) {
    struct udphdr *udp = (struct udphdr *)payload;
    EXPECT_NE(0, udp->check) << msg << ": UDP checksum 0 should be 0xffff";
    // If this is not a fragment, check the UDP length field.
    if (payload_length) {
      EXPECT_EQ(payload_length, ntohs(udp->len)) << msg << ": Incorrect UDP length\n";
    }
  }
}

void reassemble_packet(const uint8_t **fragments, const size_t lengths[], int numpackets,
                       uint8_t *reassembled, size_t *reassembled_len, const char *msg) {
  struct iphdr *ip    = nullptr;
  struct ip6_hdr *ip6 = nullptr;
  size_t total_length, pos = 0;
  uint8_t protocol = 0;
  uint8_t version  = ip_version(fragments[0]);

  for (int i = 0; i < numpackets; i++) {
    const uint8_t *packet = fragments[i];
    int len               = lengths[i];
    int headersize, payload_offset;

    ASSERT_EQ(ip_version(packet), version) << msg << ": Inconsistent fragment versions\n";
    check_packet(packet, len, "Fragment sanity check");

    switch (version) {
      case 4: {
        struct iphdr *ip_orig = (struct iphdr *)packet;
        headersize            = sizeof(*ip_orig);
        ASSERT_TRUE(is_ipv4_fragment(ip_orig))
          << msg << ": IPv4 fragment #" << i + 1 << " not a fragment\n";
        ASSERT_EQ(pos, ipv4_fragment_offset(ip_orig) * 8 + ((i != 0) ? sizeof(*ip) : 0))
          << msg << ": IPv4 fragment #" << i + 1 << ": inconsistent offset\n";

        headersize     = sizeof(*ip_orig);
        payload_offset = headersize;
        if (pos == 0) {
          ip = (struct iphdr *)reassembled;
        }
        break;
      }
      case 6: {
        struct ip6_hdr *ip6_orig = (struct ip6_hdr *)packet;
        struct ip6_frag *frag    = (struct ip6_frag *)(ip6_orig + 1);
        ASSERT_TRUE(is_ipv6_fragment(ip6_orig, len))
          << msg << ": IPv6 fragment #" << i + 1 << " not a fragment\n";
        ASSERT_EQ(pos, ipv6_fragment_offset(frag) * 8 + ((i != 0) ? sizeof(*ip6) : 0))
          << msg << ": IPv6 fragment #" << i + 1 << ": inconsistent offset\n";

        headersize     = sizeof(*ip6_orig);
        payload_offset = sizeof(*ip6_orig) + sizeof(*frag);
        if (pos == 0) {
          ip6      = (struct ip6_hdr *)reassembled;
          protocol = frag->ip6f_nxt;
        }
        break;
      }
      default:
        FAIL() << msg << ": Invalid IP version << " << version;
    }

    // If this is the first fragment, copy the header.
    if (pos == 0) {
      ASSERT_LT(headersize, (int)*reassembled_len) << msg << ": Reassembly buffer too small\n";
      memcpy(reassembled, packet, headersize);
      total_length = headersize;
      pos += headersize;
    }

    // Copy the payload.
    int payload_length = len - payload_offset;
    total_length += payload_length;
    ASSERT_LT(total_length, *reassembled_len) << msg << ": Reassembly buffer too small\n";
    memcpy(reassembled + pos, packet + payload_offset, payload_length);
    pos += payload_length;
  }

  // Fix up the reassembled headers to reflect fragmentation and length (and IPv4 checksum).
  ASSERT_EQ(total_length, pos) << msg << ": Reassembled packet length incorrect\n";
  if (ip) {
    ip->frag_off &= ~htons(IP_MF);
    ip->tot_len = htons(total_length);
    ip->check   = 0;
    ip->check   = ip_checksum(ip, sizeof(*ip));
    ASSERT_FALSE(is_ipv4_fragment(ip)) << msg << ": reassembled IPv4 packet is a fragment!\n";
  }
  if (ip6) {
    ip6->ip6_nxt  = protocol;
    ip6->ip6_plen = htons(total_length - sizeof(*ip6));
    ASSERT_FALSE(is_ipv6_fragment(ip6, ip6->ip6_plen))
      << msg << ": reassembled IPv6 packet is a fragment!\n";
  }

  *reassembled_len = total_length;
}

void check_data_matches(const void *expected, const void *actual, size_t len, const char *msg) {
  if (memcmp(expected, actual, len)) {
    // Hex dump, 20 bytes per line, one space between bytes (1 byte = 3 chars), indented by 4.
    int hexdump_len = len * 3 + (len / 20 + 1) * 5;
    char expected_hexdump[hexdump_len], actual_hexdump[hexdump_len];
    unsigned pos = 0;
    for (unsigned i = 0; i < len; i++) {
      if (i % 20 == 0) {
        snprintf(expected_hexdump + pos, hexdump_len - pos, "\n   ");
        snprintf(actual_hexdump + pos, hexdump_len - pos, "\n   ");
        pos += 4;
      }
      snprintf(expected_hexdump + pos, hexdump_len - pos, " %02x", ((uint8_t *)expected)[i]);
      snprintf(actual_hexdump + pos, hexdump_len - pos, " %02x", ((uint8_t *)actual)[i]);
      pos += 3;
    }
    FAIL() << msg << ": Data doesn't match"
           << "\n  Expected:" << (char *) expected_hexdump
           << "\n  Actual:" << (char *) actual_hexdump << "\n";
  }
}

void fix_udp_checksum(uint8_t *packet) {
  uint32_t pseudo_checksum;
  uint8_t version = ip_version(packet);
  struct udphdr *udp;
  switch (version) {
    case 4: {
      struct iphdr *ip = (struct iphdr *)packet;
      udp              = (struct udphdr *)(ip + 1);
      pseudo_checksum  = ipv4_pseudo_header_checksum(ip, ntohs(udp->len));
      break;
    }
    case 6: {
      struct ip6_hdr *ip6 = (struct ip6_hdr *)packet;
      udp                 = (struct udphdr *)(ip6 + 1);
      pseudo_checksum     = ipv6_pseudo_header_checksum(ip6, ntohs(udp->len), IPPROTO_UDP);
      break;
    }
    default:
      FAIL() << "unsupported IP version" << version << "\n";
      return;
  }

  udp->check = 0;
  udp->check = ip_checksum_finish(ip_checksum_add(pseudo_checksum, udp, ntohs(udp->len)));
}

// Testing stub for send_rawv6. The real version uses sendmsg() with a
// destination IPv6 address, and attempting to call that on our test socketpair
// fd results in EINVAL.
extern "C" void send_rawv6(int fd, clat_packet out, int iov_len) { writev(fd, out, iov_len); }

void do_translate_packet(const uint8_t *original, size_t original_len, uint8_t *out, size_t *outlen,
                         const char *msg) {
  int fds[2];
  if (socketpair(AF_UNIX, SOCK_DGRAM | SOCK_NONBLOCK, 0, fds)) {
    abort();
  }

  char foo[512];
  snprintf(foo, sizeof(foo), "%s: Invalid original packet", msg);
  check_packet(original, original_len, foo);

  int read_fd, write_fd;
  uint16_t expected_proto;
  int version = ip_version(original);
  switch (version) {
    case 4:
      expected_proto = htons(ETH_P_IPV6);
      read_fd        = fds[1];
      write_fd       = fds[0];
      break;
    case 6:
      expected_proto = htons(ETH_P_IP);
      read_fd        = fds[0];
      write_fd       = fds[1];
      break;
    default:
      FAIL() << msg << ": Unsupported IP version " << version << "\n";
      break;
  }

  translate_packet(write_fd, (version == 4), original, original_len, TP_CSUM_NONE);

  snprintf(foo, sizeof(foo), "%s: Invalid translated packet", msg);
  if (version == 6) {
    // Translating to IPv4. Expect a tun header.
    struct tun_pi new_tun_header;
    struct iovec iov[] = {
      { &new_tun_header, sizeof(new_tun_header) },
      { out, *outlen },
    };

    int len = readv(read_fd, iov, 2);
    if (len > (int)sizeof(new_tun_header)) {
      ASSERT_LT((size_t)len, *outlen) << msg << ": Translated packet buffer too small\n";
      EXPECT_EQ(expected_proto, new_tun_header.proto) << msg << "Unexpected tun proto\n";
      *outlen = len - sizeof(new_tun_header);
      check_packet(out, *outlen, msg);
    } else {
      FAIL() << msg << ": Packet was not translated: len=" << len;
      *outlen = 0;
    }
  } else {
    // Translating to IPv6. Expect raw packet.
    *outlen = read(read_fd, out, *outlen);
    check_packet(out, *outlen, msg);
  }
}

void check_translated_packet(const uint8_t *original, size_t original_len,
                             const uint8_t *expected, size_t expected_len, const char *msg) {
  uint8_t *translated = new uint8_t[MAXMRU];
  ASSERT_NE(translated, nullptr) << msg << ": Unable to allocate memory\n";
  size_t translated_len = sizeof(translated);
  do_translate_packet(original, original_len, translated, &translated_len, msg);
  EXPECT_EQ(expected_len, translated_len) << msg << ": Translated packet length incorrect\n";
  check_data_matches(expected, translated, translated_len, msg);
  delete [] translated;
}

void check_fragment_translation(const uint8_t *original[], const size_t original_lengths[],
                                const uint8_t *expected[], const size_t expected_lengths[],
                                int numfragments, const char *msg) {
  for (int i = 0; i < numfragments; i++) {
    // Check that each of the fragments translates as expected.
    char frag_msg[512];
    snprintf(frag_msg, sizeof(frag_msg), "%s: fragment #%d", msg, i + 1);
    check_translated_packet(original[i], original_lengths[i], expected[i], expected_lengths[i],
                            frag_msg);
  }

  // Sanity check that reassembling the original and translated fragments produces valid packets.
  uint8_t *reassembled = new uint8_t[MAXMRU];
  ASSERT_NE(reassembled, nullptr) << msg << ": Unable to allocate memory\n";
  size_t reassembled_len = sizeof(reassembled);
  reassemble_packet(original, original_lengths, numfragments, reassembled, &reassembled_len, msg);
  check_packet(reassembled, reassembled_len, msg);

  uint8_t *translated = new uint8_t[MAXMRU];
  ASSERT_NE(translated, nullptr) << msg << ": Unable to allocate memory\n";
  size_t translated_len = sizeof(translated);
  do_translate_packet(reassembled, reassembled_len, translated, &translated_len, msg);
  check_packet(translated, translated_len, msg);

  delete [] translated;
  delete [] reassembled;
}

int get_transport_checksum(const uint8_t *packet) {
  struct iphdr *ip;
  struct ip6_hdr *ip6;
  uint8_t protocol;
  const void *payload;

  int version = ip_version(packet);
  switch (version) {
    case 4:
      ip = (struct iphdr *)packet;
      if (is_ipv4_fragment(ip)) {
        return -1;
      }
      protocol = ip->protocol;
      payload  = ip + 1;
      break;
    case 6:
      ip6      = (struct ip6_hdr *)packet;
      protocol = ip6->ip6_nxt;
      payload  = ip6 + 1;
      break;
    default:
      return -1;
  }

  switch (protocol) {
    case IPPROTO_UDP:
      return ((struct udphdr *)payload)->check;

    case IPPROTO_TCP:
      return ((struct tcphdr *)payload)->check;

    case IPPROTO_FRAGMENT:
    default:
      return -1;
  }
}

static tun_data makeTunData() {
  // Create some fake but realistic-looking sockets so update_clat_ipv6_address doesn't balk.
  return {
    .read_fd6  = socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_IPV6)),
    .write_fd6 = socket(AF_INET6, SOCK_RAW | SOCK_NONBLOCK, IPPROTO_RAW),
    .fd4       = socket(AF_UNIX, SOCK_DGRAM, 0),
  };
}

void freeTunData(tun_data *tunnel) {
  close(tunnel->write_fd6);
  close(tunnel->read_fd6);
  close(tunnel->fd4);
}

struct clat_config Global_Clatd_Config;

class ClatdTest : public ::testing::Test {
 protected:
  static TunInterface sTun;

  virtual void SetUp() {
    inet_pton(AF_INET, kIPv4LocalAddr, &Global_Clatd_Config.ipv4_local_subnet);
    inet_pton(AF_INET6, kIPv6PlatSubnet, &Global_Clatd_Config.plat_subnet);
    memset(&Global_Clatd_Config.ipv6_local_subnet, 0, sizeof(in6_addr));
    Global_Clatd_Config.native_ipv6_interface = const_cast<char *>(sTun.name().c_str());
  }

  // Static because setting up the tun interface takes about 40ms.
  static void SetUpTestCase() { ASSERT_EQ(0, sTun.init()); }

  // Closing the socket removes the interface and IP addresses.
  static void TearDownTestCase() { sTun.destroy(); }
};

TunInterface ClatdTest::sTun;

void expect_ipv6_addr_equal(struct in6_addr *expected, struct in6_addr *actual) {
  if (!IN6_ARE_ADDR_EQUAL(expected, actual)) {
    char expected_str[INET6_ADDRSTRLEN], actual_str[INET6_ADDRSTRLEN];
    inet_ntop(AF_INET6, expected, expected_str, sizeof(expected_str));
    inet_ntop(AF_INET6, actual, actual_str, sizeof(actual_str));
    FAIL()
        << "Unexpected IPv6 address:: "
        << "\n  Expected: " << expected_str
        << "\n  Actual:   " << actual_str
        << "\n";
  }
}

TEST_F(ClatdTest, TestIPv6PrefixEqual) {
  EXPECT_TRUE(ipv6_prefix_equal(&Global_Clatd_Config.plat_subnet,
                                &Global_Clatd_Config.plat_subnet));
  EXPECT_FALSE(ipv6_prefix_equal(&Global_Clatd_Config.plat_subnet,
                                 &Global_Clatd_Config.ipv6_local_subnet));

  struct in6_addr subnet2 = Global_Clatd_Config.ipv6_local_subnet;
  EXPECT_TRUE(ipv6_prefix_equal(&Global_Clatd_Config.ipv6_local_subnet, &subnet2));
  EXPECT_TRUE(ipv6_prefix_equal(&subnet2, &Global_Clatd_Config.ipv6_local_subnet));

  subnet2.s6_addr[6] = 0xff;
  EXPECT_FALSE(ipv6_prefix_equal(&Global_Clatd_Config.ipv6_local_subnet, &subnet2));
  EXPECT_FALSE(ipv6_prefix_equal(&subnet2, &Global_Clatd_Config.ipv6_local_subnet));
}

TEST_F(ClatdTest, DetectMtu) {
  // ::1 with bottom 32 bits set to 1 is still ::1 which routes via lo with mtu of 64KiB
  ASSERT_EQ(detect_mtu(&in6addr_loopback, htonl(1), 0 /*MARK_UNSET*/), 65536);
}

TEST_F(ClatdTest, ConfigureTunIpManual) {
  // Create an interface for configure_tun_ip to configure and bring up.
  TunInterface v4Iface;
  ASSERT_EQ(0, v4Iface.init());
  struct tun_data tunnel = makeTunData();
  strlcpy(tunnel.device4, v4Iface.name().c_str(), sizeof(tunnel.device4));

  configure_tun_ip(&tunnel, "192.0.2.1" /* v4_addr */, 1472);
  EXPECT_EQ(inet_addr("192.0.2.1"), Global_Clatd_Config.ipv4_local_subnet.s_addr);

  union anyip *ip = getinterface_ip(v4Iface.name().c_str(), AF_INET);
  ASSERT_NE(nullptr, ip);
  EXPECT_EQ(inet_addr("192.0.2.1"), ip->ip4.s_addr);
  free(ip);

  v4Iface.destroy();
}

TEST_F(ClatdTest, DataSanitycheck) {
  // Sanity checks the data.
  uint8_t v4_header[] = { IPV4_UDP_HEADER };
  ASSERT_EQ(sizeof(struct iphdr), sizeof(v4_header)) << "Test IPv4 header: incorrect length\n";

  uint8_t v6_header[] = { IPV6_UDP_HEADER };
  ASSERT_EQ(sizeof(struct ip6_hdr), sizeof(v6_header)) << "Test IPv6 header: incorrect length\n";

  uint8_t udp_header[] = { UDP_HEADER };
  ASSERT_EQ(sizeof(struct udphdr), sizeof(udp_header)) << "Test UDP header: incorrect length\n";

  // Sanity checks check_packet.
  struct udphdr *udp;
  uint8_t v4_udp_packet[] = { IPV4_UDP_HEADER UDP_HEADER PAYLOAD };
  udp                     = (struct udphdr *)(v4_udp_packet + sizeof(struct iphdr));
  fix_udp_checksum(v4_udp_packet);
  ASSERT_EQ(kUdpV4Checksum, udp->check) << "UDP/IPv4 packet checksum sanity check\n";
  check_packet(v4_udp_packet, sizeof(v4_udp_packet), "UDP/IPv4 packet sanity check");

  uint8_t v6_udp_packet[] = { IPV6_UDP_HEADER UDP_HEADER PAYLOAD };
  udp                     = (struct udphdr *)(v6_udp_packet + sizeof(struct ip6_hdr));
  fix_udp_checksum(v6_udp_packet);
  ASSERT_EQ(kUdpV6Checksum, udp->check) << "UDP/IPv6 packet checksum sanity check\n";
  check_packet(v6_udp_packet, sizeof(v6_udp_packet), "UDP/IPv6 packet sanity check");

  uint8_t ipv4_ping[] = { IPV4_ICMP_HEADER IPV4_PING PAYLOAD };
  check_packet(ipv4_ping, sizeof(ipv4_ping), "IPv4 ping sanity check");

  uint8_t ipv6_ping[] = { IPV6_ICMPV6_HEADER IPV6_PING PAYLOAD };
  check_packet(ipv6_ping, sizeof(ipv6_ping), "IPv6 ping sanity check");

  // Sanity checks reassemble_packet.
  uint8_t *reassembled = new uint8_t[MAXMRU];
  ASSERT_NE(reassembled, nullptr) << ": Unable to allocate memory\n";
  size_t total_length = sizeof(reassembled);
  reassemble_packet(kIPv4Fragments, kIPv4FragLengths, ARRAYSIZE(kIPv4Fragments), reassembled,
                    &total_length, "Reassembly sanity check");
  check_packet(reassembled, total_length, "IPv4 Reassembled packet is valid");
  ASSERT_EQ(sizeof(kReassembledIPv4), total_length) << "IPv4 reassembly sanity check: length\n";
  ASSERT_TRUE(!is_ipv4_fragment((struct iphdr *)reassembled))
    << "Sanity check: reassembled packet is a fragment!\n";
  check_data_matches(kReassembledIPv4, reassembled, total_length, "IPv4 reassembly sanity check");

  total_length = sizeof(reassembled);
  reassemble_packet(kIPv6Fragments, kIPv6FragLengths, ARRAYSIZE(kIPv6Fragments), reassembled,
                    &total_length, "IPv6 reassembly sanity check");
  ASSERT_TRUE(!is_ipv6_fragment((struct ip6_hdr *)reassembled, total_length))
    << "Sanity check: reassembled packet is a fragment!\n";
  check_packet(reassembled, total_length, "IPv6 Reassembled packet is valid");
  delete [] reassembled;
}

TEST_F(ClatdTest, PseudoChecksum) {
  uint32_t pseudo_checksum;

  uint8_t v4_header[]        = { IPV4_UDP_HEADER };
  uint8_t v4_pseudo_header[] = { IPV4_PSEUDOHEADER(v4_header, UDP_LEN) };
  pseudo_checksum            = ipv4_pseudo_header_checksum((struct iphdr *)v4_header, UDP_LEN);
  EXPECT_EQ(ip_checksum_finish(pseudo_checksum),
            ip_checksum(v4_pseudo_header, sizeof(v4_pseudo_header)))
    << "ipv4_pseudo_header_checksum incorrect\n";

  uint8_t v6_header[]        = { IPV6_UDP_HEADER };
  uint8_t v6_pseudo_header[] = { IPV6_PSEUDOHEADER(v6_header, IPPROTO_UDP, UDP_LEN) };
  pseudo_checksum = ipv6_pseudo_header_checksum((struct ip6_hdr *)v6_header, UDP_LEN, IPPROTO_UDP);
  EXPECT_EQ(ip_checksum_finish(pseudo_checksum),
            ip_checksum(v6_pseudo_header, sizeof(v6_pseudo_header)))
    << "ipv6_pseudo_header_checksum incorrect\n";
}

TEST_F(ClatdTest, TransportChecksum) {
  uint8_t udphdr[]  = { UDP_HEADER };
  uint8_t payload[] = { PAYLOAD };
  EXPECT_EQ(kUdpPartialChecksum, ip_checksum_add(0, udphdr, sizeof(udphdr)))
    << "UDP partial checksum\n";
  EXPECT_EQ(kPayloadPartialChecksum, ip_checksum_add(0, payload, sizeof(payload)))
    << "Payload partial checksum\n";

  uint8_t ip[]             = { IPV4_UDP_HEADER };
  uint8_t ip6[]            = { IPV6_UDP_HEADER };
  uint32_t ipv4_pseudo_sum = ipv4_pseudo_header_checksum((struct iphdr *)ip, UDP_LEN);
  uint32_t ipv6_pseudo_sum =
    ipv6_pseudo_header_checksum((struct ip6_hdr *)ip6, UDP_LEN, IPPROTO_UDP);

  EXPECT_NE(0, ipv4_pseudo_sum);
  EXPECT_NE(0, ipv6_pseudo_sum);
  EXPECT_EQ(0x3ad0U, ipv4_pseudo_sum % 0xFFFF) << "IPv4 pseudo-checksum sanity check\n";
  EXPECT_EQ(0x644dU, ipv6_pseudo_sum % 0xFFFF) << "IPv6 pseudo-checksum sanity check\n";
  EXPECT_EQ(
      kUdpV4Checksum,
      ip_checksum_finish(ipv4_pseudo_sum + kUdpPartialChecksum + kPayloadPartialChecksum))
      << "Unexpected UDP/IPv4 checksum\n";
  EXPECT_EQ(
      kUdpV6Checksum,
      ip_checksum_finish(ipv6_pseudo_sum + kUdpPartialChecksum + kPayloadPartialChecksum))
      << "Unexpected UDP/IPv6 checksum\n";

  EXPECT_EQ(kUdpV6Checksum,
      ip_checksum_adjust(kUdpV4Checksum, ipv4_pseudo_sum, ipv6_pseudo_sum))
      << "Adjust IPv4/UDP checksum to IPv6\n";
  EXPECT_EQ(kUdpV4Checksum,
      ip_checksum_adjust(kUdpV6Checksum, ipv6_pseudo_sum, ipv4_pseudo_sum))
      << "Adjust IPv6/UDP checksum to IPv4\n";
}

TEST_F(ClatdTest, AdjustChecksum) {
  struct checksum_data {
    uint16_t checksum;
    uint32_t old_hdr_sum;
    uint32_t new_hdr_sum;
    uint16_t result;
  } DATA[] = {
    { 0x1423, 0xb8ec, 0x2d757, 0xf5b5 },
    { 0xf5b5, 0x2d757, 0xb8ec, 0x1423 },
    { 0xdd2f, 0x5555, 0x3285, 0x0000 },
    { 0x1215, 0x5560, 0x15560 + 20, 0x1200 },
    { 0xd0c7, 0x3ad0, 0x2644b, 0xa74a },
  };
  unsigned i = 0;

  for (i = 0; i < ARRAYSIZE(DATA); i++) {
    struct checksum_data *data = DATA + i;
    uint16_t result = ip_checksum_adjust(data->checksum, data->old_hdr_sum, data->new_hdr_sum);
    EXPECT_EQ(result, data->result)
        << "Incorrect checksum" << std::showbase << std::hex
        << "\n  Expected: " << data->result
        << "\n  Actual:   " << result
        << "\n    checksum=" << data->checksum
        << " old_sum=" << data->old_hdr_sum << " new_sum=" << data->new_hdr_sum << "\n";
  }
}

TEST_F(ClatdTest, Translate) {
  // This test uses hardcoded packets so the clatd address must be fixed.
  inet_pton(AF_INET6, kIPv6LocalAddr, &Global_Clatd_Config.ipv6_local_subnet);

  uint8_t udp_ipv4[] = { IPV4_UDP_HEADER UDP_HEADER PAYLOAD };
  uint8_t udp_ipv6[] = { IPV6_UDP_HEADER UDP_HEADER PAYLOAD };
  fix_udp_checksum(udp_ipv4);
  fix_udp_checksum(udp_ipv6);
  check_translated_packet(udp_ipv4, sizeof(udp_ipv4), udp_ipv6, sizeof(udp_ipv6),
                          "UDP/IPv4 -> UDP/IPv6 translation");
  check_translated_packet(udp_ipv6, sizeof(udp_ipv6), udp_ipv4, sizeof(udp_ipv4),
                          "UDP/IPv6 -> UDP/IPv4 translation");

  uint8_t ipv4_ping[] = { IPV4_ICMP_HEADER IPV4_PING PAYLOAD };
  uint8_t ipv6_ping[] = { IPV6_ICMPV6_HEADER IPV6_PING PAYLOAD };
  check_translated_packet(ipv4_ping, sizeof(ipv4_ping), ipv6_ping, sizeof(ipv6_ping),
                          "ICMP->ICMPv6 translation");
  check_translated_packet(ipv6_ping, sizeof(ipv6_ping), ipv4_ping, sizeof(ipv4_ping),
                          "ICMPv6->ICMP translation");
}

TEST_F(ClatdTest, Fragmentation) {
  // This test uses hardcoded packets so the clatd address must be fixed.
  inet_pton(AF_INET6, kIPv6LocalAddr, &Global_Clatd_Config.ipv6_local_subnet);

  check_fragment_translation(kIPv4Fragments, kIPv4FragLengths, kIPv6Fragments, kIPv6FragLengths,
                             ARRAYSIZE(kIPv4Fragments), "IPv4->IPv6 fragment translation");

  check_fragment_translation(kIPv6Fragments, kIPv6FragLengths, kIPv4Fragments, kIPv4FragLengths,
                             ARRAYSIZE(kIPv6Fragments), "IPv6->IPv4 fragment translation");
}

// picks a random interface ID that is checksum neutral with the IPv4 address and the NAT64 prefix
void gen_random_iid(struct in6_addr *myaddr, struct in_addr *ipv4_local_subnet,
                    struct in6_addr *plat_subnet) {
  // Fill last 8 bytes of IPv6 address with random bits.
  arc4random_buf(&myaddr->s6_addr[8], 8);

  // Make the IID checksum-neutral. That is, make it so that:
  //   checksum(Local IPv4 | Remote IPv4) = checksum(Local IPv6 | Remote IPv6)
  // in other words (because remote IPv6 = NAT64 prefix | Remote IPv4):
  //   checksum(Local IPv4) = checksum(Local IPv6 | NAT64 prefix)
  // Do this by adjusting the two bytes in the middle of the IID.

  uint16_t middlebytes = (myaddr->s6_addr[11] << 8) + myaddr->s6_addr[12];

  uint32_t c1 = ip_checksum_add(0, ipv4_local_subnet, sizeof(*ipv4_local_subnet));
  uint32_t c2 = ip_checksum_add(0, plat_subnet, sizeof(*plat_subnet)) +
                ip_checksum_add(0, myaddr, sizeof(*myaddr));

  uint16_t delta      = ip_checksum_adjust(middlebytes, c1, c2);
  myaddr->s6_addr[11] = delta >> 8;
  myaddr->s6_addr[12] = delta & 0xff;
}

void check_translate_checksum_neutral(const uint8_t *original, size_t original_len,
                                      size_t expected_len, const char *msg) {
  uint8_t *translated = new uint8_t[MAXMRU];
  ASSERT_NE(translated, nullptr) << msg << ": Unable to allocate memory\n";
  size_t translated_len = sizeof(translated);
  do_translate_packet(original, original_len, translated, &translated_len, msg);
  EXPECT_EQ(expected_len, translated_len) << msg << ": Translated packet length incorrect\n";
  // do_translate_packet already checks packets for validity and verifies the checksum.
  int original_check   = get_transport_checksum(original);
  int translated_check = get_transport_checksum(translated);
  ASSERT_NE(-1, original_check);
  ASSERT_NE(-1, translated_check);
  ASSERT_EQ(original_check, translated_check)
    << "Not checksum neutral: original and translated checksums differ\n";
  delete [] translated;
}

TEST_F(ClatdTest, TranslateChecksumNeutral) {
  // Generate a random clat IPv6 address and check that translation is checksum-neutral.
  ASSERT_TRUE(inet_pton(AF_INET6, "2001:db8:1:2:f076:ae99:124e:aa54",
                        &Global_Clatd_Config.ipv6_local_subnet));

  gen_random_iid(&Global_Clatd_Config.ipv6_local_subnet, &Global_Clatd_Config.ipv4_local_subnet,
                 &Global_Clatd_Config.plat_subnet);

  ASSERT_NE(htonl((uint32_t)0x00000464), Global_Clatd_Config.ipv6_local_subnet.s6_addr32[3]);
  ASSERT_NE((uint32_t)0, Global_Clatd_Config.ipv6_local_subnet.s6_addr32[3]);

  // Check that translating UDP packets is checksum-neutral. First, IPv4.
  uint8_t udp_ipv4[] = { IPV4_UDP_HEADER UDP_HEADER PAYLOAD };
  fix_udp_checksum(udp_ipv4);
  check_translate_checksum_neutral(udp_ipv4, sizeof(udp_ipv4), sizeof(udp_ipv4) + 20,
                                   "UDP/IPv4 -> UDP/IPv6 checksum neutral");

  // Now try IPv6.
  uint8_t udp_ipv6[] = { IPV6_UDP_HEADER UDP_HEADER PAYLOAD };
  // The test packet uses the static IID, not the random IID. Fix up the source address.
  struct ip6_hdr *ip6 = (struct ip6_hdr *)udp_ipv6;
  memcpy(&ip6->ip6_src, &Global_Clatd_Config.ipv6_local_subnet, sizeof(ip6->ip6_src));
  fix_udp_checksum(udp_ipv6);
  check_translate_checksum_neutral(udp_ipv4, sizeof(udp_ipv4), sizeof(udp_ipv4) + 20,
                                   "UDP/IPv4 -> UDP/IPv6 checksum neutral");
}

TEST_F(ClatdTest, GetInterfaceIp) {
  union anyip *ip = getinterface_ip(sTun.name().c_str(), AF_INET6);
  ASSERT_NE(nullptr, ip);
  in6_addr expected = sTun.srcAddr();
  in6_addr actual   = ip->ip6;
  expect_ipv6_addr_equal(&expected, &actual);
}

void expectSocketBound(int ifindex, int sock) {
  // Check that the packet socket is bound to the interface. We can't check the socket filter
  // because there is no way to fetch it from the kernel.
  sockaddr_ll sll;
  socklen_t len = sizeof(sll);
  ASSERT_EQ(0, getsockname(sock, reinterpret_cast<sockaddr *>(&sll), &len));
  EXPECT_EQ(htons(ETH_P_IPV6), sll.sll_protocol);
  EXPECT_EQ(ifindex, sll.sll_ifindex);
}

TEST_F(ClatdTest, ConfigureIpv6Address) {
  struct tun_data tunnel = makeTunData();

  ASSERT_TRUE(IN6_IS_ADDR_UNSPECIFIED(&Global_Clatd_Config.ipv6_local_subnet));

  const char *addrStr = "2001:db8::f00";
  in6_addr addr;
  ASSERT_EQ(1, inet_pton(AF_INET6, addrStr, &addr));
  ASSERT_EQ(1, configure_clat_ipv6_address(&tunnel, sTun.name().c_str(), addrStr));

  EXPECT_EQ(htonl(0x20010db8), Global_Clatd_Config.ipv6_local_subnet.s6_addr32[0]);
  EXPECT_EQ(htonl(0x00000000), Global_Clatd_Config.ipv6_local_subnet.s6_addr32[1]);
  EXPECT_EQ(htonl(0x00000000), Global_Clatd_Config.ipv6_local_subnet.s6_addr32[2]);
  EXPECT_EQ(htonl(0x00000f00), Global_Clatd_Config.ipv6_local_subnet.s6_addr32[3]);

  // Check that the packet socket is bound to the interface. We can't check the socket filter
  // because there is no way to fetch it from the kernel.
  sockaddr_ll sll;
  socklen_t len = sizeof(sll);
  ASSERT_EQ(0, getsockname(tunnel.read_fd6, reinterpret_cast<sockaddr *>(&sll), &len));
  EXPECT_EQ(htons(ETH_P_IPV6), sll.sll_protocol);
  EXPECT_EQ(sll.sll_ifindex, sTun.ifindex());

  expectSocketBound(sTun.ifindex(), tunnel.read_fd6);

  freeTunData(&tunnel);
}

TEST_F(ClatdTest, Ipv6AddressChanged) {
  // Configure the clat IPv6 address.
  struct tun_data tunnel = {
    .read_fd6  = socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_IPV6)),
    .write_fd6 = socket(AF_INET6, SOCK_RAW | SOCK_NONBLOCK, IPPROTO_RAW),
  };
  const char *ifname = sTun.name().c_str();

  in6_addr myaddr = sTun.srcAddr();
  gen_random_iid(&myaddr, &Global_Clatd_Config.ipv4_local_subnet, &Global_Clatd_Config.plat_subnet);
  char addrstr[INET6_ADDRSTRLEN];
  ASSERT_NE(nullptr, inet_ntop(AF_INET6, &myaddr, addrstr, sizeof(addrstr)));

  ASSERT_EQ(1, configure_clat_ipv6_address(&tunnel, ifname, addrstr));
  EXPECT_EQ(0, ipv6_address_changed(ifname));
  EXPECT_EQ(0, ipv6_address_changed(ifname));

  // Change the IP address on the tun interface to a new prefix.
  char srcaddr[INET6_ADDRSTRLEN];
  char dstaddr[INET6_ADDRSTRLEN];
  ASSERT_NE(nullptr, inet_ntop(AF_INET6, &sTun.srcAddr(), srcaddr, sizeof(srcaddr)));
  ASSERT_NE(nullptr, inet_ntop(AF_INET6, &sTun.dstAddr(), dstaddr, sizeof(dstaddr)));
  EXPECT_EQ(0, ifc_del_address(ifname, srcaddr, 64));
  EXPECT_EQ(0, ifc_del_address(ifname, dstaddr, 64));

  // Check that we can tell that the address has changed.
  EXPECT_EQ(0, ifc_add_address(ifname, "2001:db8::1:2", 64));
  EXPECT_EQ(1, ipv6_address_changed(ifname));
  EXPECT_EQ(1, ipv6_address_changed(ifname));

  // Restore the tun interface configuration.
  sTun.destroy();
  ASSERT_EQ(0, sTun.init());
}