diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..d97975c
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,3 @@
+third_party {
+  license_type: NOTICE
+}
diff --git a/clatd.c b/clatd.c
index 3f9dc71..50693f5 100644
--- a/clatd.c
+++ b/clatd.c
@@ -109,52 +109,15 @@
   return 1;
 }
 
-/* function: ipv4_address_generate
- * picks a free IPv4 address from the local subnet or exits if there are no free addresses
- *   returns: the IPv4 address as an in_addr_t
- */
-static in_addr_t ipv4_address_generate() {
-  // Pick an IPv4 address to use by finding a free address in the configured prefix. Technically,
-  // there is a race here - if another clatd calls config_select_ipv4_address after we do, but
-  // before we call add_address, it can end up having the same IP address as we do. But the time
-  // window in which this can happen is extremely small, and even if we end up with a duplicate
-  // address, the only damage is that IPv4 TCP connections won't be reset until both interfaces go
-  // down.
-  in_addr_t localaddr = config_select_ipv4_address(&Global_Clatd_Config.ipv4_local_subnet,
-                                                   Global_Clatd_Config.ipv4_local_prefixlen);
-  if (localaddr == INADDR_NONE) {
-    logmsg(ANDROID_LOG_FATAL, "No free IPv4 address in %s/%d",
-           inet_ntoa(Global_Clatd_Config.ipv4_local_subnet),
-           Global_Clatd_Config.ipv4_local_prefixlen);
-    exit(1);
-  }
-  return localaddr;
-}
-
-/* function: ipv4_address_from_cmdline
- * configures the IPv4 address specified on the command line, or exits if the address is not valid
- *   v4_addr - a string, the IPv4 address
- *   returns: the IPv4 address as an in_addr_t
- */
-static in_addr_t ipv4_address_from_cmdline(const char *v4_addr) {
-  in_addr_t localaddr;
-  if (!inet_pton(AF_INET, v4_addr, &localaddr)) {
-    logmsg(ANDROID_LOG_FATAL, "Invalid IPv4 address %s", v4_addr);
-    exit(1);
-  }
-  return localaddr;
-}
-
 /* function: configure_tun_ip
  * configures the ipv4 and ipv6 addresses on the tunnel interface
  *   tunnel - tun device data
  *   mtu    - mtu of tun device
  */
 void configure_tun_ip(const struct tun_data *tunnel, const char *v4_addr, int mtu) {
-  if (v4_addr) {
-    Global_Clatd_Config.ipv4_local_subnet.s_addr = ipv4_address_from_cmdline(v4_addr);
-  } else {
-    Global_Clatd_Config.ipv4_local_subnet.s_addr = ipv4_address_generate();
+  if (!v4_addr || !inet_pton(AF_INET, v4_addr, &Global_Clatd_Config.ipv4_local_subnet.s_addr)) {
+    logmsg(ANDROID_LOG_FATAL, "Invalid IPv4 address %s", v4_addr);
+    exit(1);
   }
 
   char addrstr[INET_ADDRSTRLEN];
@@ -272,43 +235,6 @@
   }
 }
 
-/* function: clat_ipv6_address_from_interface
- * picks the clat IPv6 address based on the interface address
- *   interface - uplink interface name
- *   returns: 1 on success, 0 on failure
- */
-static int clat_ipv6_address_from_interface(const char *interface) {
-  union anyip *interface_ip;
-
-  // TODO: check that the prefix length is /64.
-  interface_ip = getinterface_ip(interface, AF_INET6);
-  if (!interface_ip) {
-    logmsg(ANDROID_LOG_ERROR, "Unable to find an IPv6 address on interface %s", interface);
-    return 0;
-  }
-
-  // Generate an interface ID.
-  config_generate_local_ipv6_subnet(&interface_ip->ip6);
-
-  Global_Clatd_Config.ipv6_local_subnet = interface_ip->ip6;
-  free(interface_ip);
-  return 1;
-}
-
-/* function: clat_ipv6_address_from_cmdline
- * parses the clat IPv6 address from the command line
- *   v4_addr - a string, the IPv6 address
- *   returns: 1 on success, 0 on failure
- */
-static int clat_ipv6_address_from_cmdline(const char *v6_addr) {
-  if (!inet_pton(AF_INET6, v6_addr, &Global_Clatd_Config.ipv6_local_subnet)) {
-    logmsg(ANDROID_LOG_FATAL, "Invalid source address %s", v6_addr);
-    return 0;
-  }
-
-  return 1;
-}
-
 /* function: configure_clat_ipv6_address
  * picks the clat IPv6 address and configures packet translation to use it.
  *   tunnel - tun device data
@@ -317,13 +243,10 @@
  */
 int configure_clat_ipv6_address(const struct tun_data *tunnel, const char *interface,
                                 const char *v6_addr) {
-  int ret;
-  if (v6_addr) {
-    ret = clat_ipv6_address_from_cmdline(v6_addr);
-  } else {
-    ret = clat_ipv6_address_from_interface(interface);
+  if (!v6_addr || !inet_pton(AF_INET6, v6_addr, &Global_Clatd_Config.ipv6_local_subnet)) {
+    logmsg(ANDROID_LOG_FATAL, "Invalid source address %s", v6_addr);
+    return 0;
   }
-  if (!ret) return 0;
 
   char addrstr[INET6_ADDRSTRLEN];
   inet_ntop(AF_INET6, &Global_Clatd_Config.ipv6_local_subnet, addrstr, sizeof(addrstr));
diff --git a/clatd.conf b/clatd.conf
index 1025fb2..36fcafd 100644
--- a/clatd.conf
+++ b/clatd.conf
@@ -1,13 +1 @@
-# Host IID to use as the source of CLAT traffic.
-# This is a /128 taken out of the /64 on the parent interface.
-# A host IID of :: means to generate a checksum-neutral, random IID.
-ipv6_host_id ::
-
-# IPv4 address configuration to use when selecting a host address. The first
-# clat daemon started will use the address specified by ipv4_local_subnet. If
-# more than one daemon is run at the same time, subsequent daemons will use
-# other addresses in the prefix of length ipv4_local prefixlen that contains
-# ipv4_local_subnet. The default is to use the IANA-assigned range 192.0.0.0/29,
-# which allows up to 8 clat daemons (.4, .5, .6, .7, .0, .1, .2, .3).
-ipv4_local_subnet 192.0.0.4
-ipv4_local_prefixlen 29
+temporary_placeholder 0
diff --git a/clatd_test.cpp b/clatd_test.cpp
index 5de7b63..e24b036 100644
--- a/clatd_test.cpp
+++ b/clatd_test.cpp
@@ -585,8 +585,6 @@
     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.ipv6_host_id    = in6addr_any;
-    Global_Clatd_Config.use_dynamic_iid = 1;
     Global_Clatd_Config.default_pdp_interface = const_cast<char *>(sTun.name().c_str());
   }
 
@@ -627,183 +625,12 @@
   EXPECT_FALSE(ipv6_prefix_equal(&subnet2, &Global_Clatd_Config.ipv6_local_subnet));
 }
 
-int count_onebits(const void *data, size_t size) {
-  int onebits = 0;
-  for (size_t pos = 0; pos < size; pos++) {
-    uint8_t *byte = ((uint8_t *)data) + pos;
-    for (int shift = 0; shift < 8; shift++) {
-      onebits += (*byte >> shift) & 1;
-    }
-  }
-  return onebits;
-}
-
-TEST_F(ClatdTest, TestCountOnebits) {
-  uint64_t i;
-  i = 1;
-  ASSERT_EQ(1, count_onebits(&i, sizeof(i)));
-  i <<= 61;
-  ASSERT_EQ(1, count_onebits(&i, sizeof(i)));
-  i |= ((uint64_t)1 << 33);
-  ASSERT_EQ(2, count_onebits(&i, sizeof(i)));
-  i = 0xf1000202020000f0;
-  ASSERT_EQ(5 + 1 + 1 + 1 + 4, count_onebits(&i, sizeof(i)));
-}
-
-TEST_F(ClatdTest, TestGenIIDConfigured) {
-  struct in6_addr myaddr, expected;
-  Global_Clatd_Config.use_dynamic_iid = 0;
-  ASSERT_TRUE(inet_pton(AF_INET6, "::bad:ace:d00d", &Global_Clatd_Config.ipv6_host_id));
-  ASSERT_TRUE(inet_pton(AF_INET6, "2001:db8:1:2:0:bad:ace:d00d", &expected));
-  ASSERT_TRUE(inet_pton(AF_INET6, "2001:db8:1:2:f076:ae99:124e:aa54", &myaddr));
-  config_generate_local_ipv6_subnet(&myaddr);
-  expect_ipv6_addr_equal(&expected, &myaddr);
-
-  Global_Clatd_Config.use_dynamic_iid = 1;
-  config_generate_local_ipv6_subnet(&myaddr);
-  EXPECT_FALSE(IN6_ARE_ADDR_EQUAL(&expected, &myaddr));
-}
-
-TEST_F(ClatdTest, TestGenIIDRandom) {
-  struct in6_addr interface_ipv6;
-  ASSERT_TRUE(inet_pton(AF_INET6, "2001:db8:1:2:f076:ae99:124e:aa54", &interface_ipv6));
-  Global_Clatd_Config.ipv6_host_id = in6addr_any;
-
-  // Generate a boatload of random IIDs.
-  int onebits       = 0;
-  uint64_t prev_iid = 0;
-  for (int i = 0; i < 100000; i++) {
-    struct in6_addr myaddr = interface_ipv6;
-
-    config_generate_local_ipv6_subnet(&myaddr);
-
-    // Check the generated IP address is in the same prefix as the interface IPv6 address.
-    EXPECT_TRUE(ipv6_prefix_equal(&interface_ipv6, &myaddr));
-
-    // Check that consecutive IIDs are not the same.
-    uint64_t iid = *(uint64_t *)(&myaddr.s6_addr[8]);
-    ASSERT_TRUE(iid != prev_iid)
-        << "Two consecutive random IIDs are the same: "
-        << std::showbase << std::hex
-        << iid << "\n";
-    prev_iid = iid;
-
-    // Check that the IID is checksum-neutral with the NAT64 prefix and the
-    // local prefix.
-    struct in_addr *ipv4addr     = &Global_Clatd_Config.ipv4_local_subnet;
-    struct in6_addr *plat_subnet = &Global_Clatd_Config.plat_subnet;
-
-    uint16_t c1 = ip_checksum_finish(ip_checksum_add(0, ipv4addr, sizeof(*ipv4addr)));
-    uint16_t c2 = ip_checksum_finish(ip_checksum_add(0, plat_subnet, sizeof(*plat_subnet)) +
-                                     ip_checksum_add(0, &myaddr, sizeof(myaddr)));
-
-    if (c1 != c2) {
-      char myaddr_str[INET6_ADDRSTRLEN], plat_str[INET6_ADDRSTRLEN], ipv4_str[INET6_ADDRSTRLEN];
-      inet_ntop(AF_INET6, &myaddr, myaddr_str, sizeof(myaddr_str));
-      inet_ntop(AF_INET6, plat_subnet, plat_str, sizeof(plat_str));
-      inet_ntop(AF_INET, ipv4addr, ipv4_str, sizeof(ipv4_str));
-      FAIL()
-          << "Bad IID: " << myaddr_str
-          << " not checksum-neutral with " << ipv4_str << " and " << plat_str
-          << std::showbase << std::hex
-          << "\n  IPv4 checksum: " << c1
-          << "\n  IPv6 checksum: " << c2
-          << "\n";
-    }
-
-    // Check that IIDs are roughly random and use all the bits by counting the
-    // total number of bits set to 1 in a random sample of 100000 generated IIDs.
-    onebits += count_onebits(&iid, sizeof(iid));
-  }
-  EXPECT_LE(3190000, onebits);
-  EXPECT_GE(3210000, onebits);
-}
-
-extern "C" addr_free_func config_is_ipv4_address_free;
-int never_free(in_addr_t /* addr */) { return 0; }
-int always_free(in_addr_t /* addr */) { return 1; }
-int only2_free(in_addr_t addr) { return (ntohl(addr) & 0xff) == 2; }
-int over6_free(in_addr_t addr) { return (ntohl(addr) & 0xff) >= 6; }
-int only10_free(in_addr_t addr) { return (ntohl(addr) & 0xff) == 10; }
-
-TEST_F(ClatdTest, SelectIPv4Address) {
-  struct in_addr addr;
-
-  inet_pton(AF_INET, kIPv4LocalAddr, &addr);
-
-  addr_free_func orig_config_is_ipv4_address_free = config_is_ipv4_address_free;
-
-  // If no addresses are free, return INADDR_NONE.
-  config_is_ipv4_address_free = never_free;
-  EXPECT_EQ(INADDR_NONE, config_select_ipv4_address(&addr, 29));
-  EXPECT_EQ(INADDR_NONE, config_select_ipv4_address(&addr, 16));
-
-  // If the configured address is free, pick that. But a prefix that's too big is invalid.
-  config_is_ipv4_address_free = always_free;
-  EXPECT_EQ(inet_addr(kIPv4LocalAddr), config_select_ipv4_address(&addr, 29));
-  EXPECT_EQ(inet_addr(kIPv4LocalAddr), config_select_ipv4_address(&addr, 20));
-  EXPECT_EQ(INADDR_NONE, config_select_ipv4_address(&addr, 15));
-
-  // A prefix length of 32 works, but anything above it is invalid.
-  EXPECT_EQ(inet_addr(kIPv4LocalAddr), config_select_ipv4_address(&addr, 32));
-  EXPECT_EQ(INADDR_NONE, config_select_ipv4_address(&addr, 33));
-
-  // If another address is free, pick it.
-  config_is_ipv4_address_free = over6_free;
-  EXPECT_EQ(inet_addr("192.0.0.6"), config_select_ipv4_address(&addr, 29));
-
-  // Check that we wrap around to addresses that are lower than the first address.
-  config_is_ipv4_address_free = only2_free;
-  EXPECT_EQ(inet_addr("192.0.0.2"), config_select_ipv4_address(&addr, 29));
-  EXPECT_EQ(INADDR_NONE, config_select_ipv4_address(&addr, 30));
-
-  // If a free address exists outside the prefix, we don't pick it.
-  config_is_ipv4_address_free = only10_free;
-  EXPECT_EQ(INADDR_NONE, config_select_ipv4_address(&addr, 29));
-  EXPECT_EQ(inet_addr("192.0.0.10"), config_select_ipv4_address(&addr, 24));
-
-  // Now try using the real function which sees if IP addresses are free using bind().
-  // Assume that the machine running the test has the address 127.0.0.1, but not 8.8.8.8.
-  config_is_ipv4_address_free = orig_config_is_ipv4_address_free;
-  addr.s_addr                 = inet_addr("8.8.8.8");
-  EXPECT_EQ(inet_addr("8.8.8.8"), config_select_ipv4_address(&addr, 29));
-
-  addr.s_addr = inet_addr("127.0.0.1");
-  EXPECT_EQ(inet_addr("127.0.0.2"), config_select_ipv4_address(&addr, 29));
-}
-
 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, ConfigureTunIp) {
-  addr_free_func orig_config_is_ipv4_address_free = config_is_ipv4_address_free;
-  config_is_ipv4_address_free                     = over6_free;
-
-  Global_Clatd_Config.ipv4_local_prefixlen = 29;
-
-  // 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, nullptr /* v4_addr */, 1472);
-  EXPECT_EQ(inet_addr("192.0.0.6"), Global_Clatd_Config.ipv4_local_subnet.s_addr);
-
-  union anyip *ip = getinterface_ip(v4Iface.name().c_str(), AF_INET);
-  EXPECT_EQ(inet_addr("192.0.0.6"), ip->ip4.s_addr);
-  free(ip);
-
-  config_is_ipv4_address_free = orig_config_is_ipv4_address_free;
-  v4Iface.destroy();
-}
-
 TEST_F(ClatdTest, ConfigureTunIpManual) {
-  addr_free_func orig_config_is_ipv4_address_free = config_is_ipv4_address_free;
-  config_is_ipv4_address_free                     = over6_free;
-
   Global_Clatd_Config.ipv4_local_prefixlen = 29;
 
   // Create an interface for configure_tun_ip to configure and bring up.
@@ -820,7 +647,6 @@
   EXPECT_EQ(inet_addr("192.0.2.1"), ip->ip4.s_addr);
   free(ip);
 
-  config_is_ipv4_address_free = orig_config_is_ipv4_address_free;
   v4Iface.destroy();
 }
 
@@ -986,6 +812,29 @@
                              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[MAXMTU];
@@ -1003,10 +852,12 @@
 
 TEST_F(ClatdTest, TranslateChecksumNeutral) {
   // Generate a random clat IPv6 address and check that translation is checksum-neutral.
-  Global_Clatd_Config.ipv6_host_id = in6addr_any;
   ASSERT_TRUE(inet_pton(AF_INET6, "2001:db8:1:2:f076:ae99:124e:aa54",
                         &Global_Clatd_Config.ipv6_local_subnet));
-  config_generate_local_ipv6_subnet(&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]);
 
@@ -1079,7 +930,13 @@
     .write_fd6 = socket(AF_INET6, SOCK_RAW | SOCK_NONBLOCK, IPPROTO_RAW),
   };
   const char *ifname = sTun.name().c_str();
-  ASSERT_EQ(1, configure_clat_ipv6_address(&tunnel, ifname, nullptr));
+
+  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));
 
diff --git a/config.c b/config.c
index db0abc8..554db0e 100644
--- a/config.c
+++ b/config.c
@@ -35,66 +35,6 @@
 
 struct clat_config Global_Clatd_Config;
 
-/* function: config_item_str
- * locates the config item and returns the pointer to a string, or NULL on failure.  Caller frees
- * pointer
- *   root       - parsed configuration
- *   item_name  - name of config item to locate
- *   defaultvar - value to use if config item isn't present
- */
-char *config_item_str(cnode *root, const char *item_name, const char *defaultvar) {
-  const char *tmp;
-
-  if (!(tmp = config_str(root, item_name, defaultvar))) {
-    logmsg(ANDROID_LOG_FATAL, "%s config item needed", item_name);
-    return NULL;
-  }
-  return strdup(tmp);
-}
-
-/* function: config_item_int16_t
- * locates the config item, parses the integer, and returns the pointer ret_val_ptr, or NULL on
- * failure
- *   root        - parsed configuration
- *   item_name   - name of config item to locate
- *   defaultvar  - value to use if config item isn't present
- *   ret_val_ptr - pointer for return value storage
- */
-int16_t *config_item_int16_t(cnode *root, const char *item_name, const char *defaultvar,
-                             int16_t *ret_val_ptr) {
-  const char *tmp;
-  char *endptr;
-  long int conf_int;
-
-  if (!(tmp = config_str(root, item_name, defaultvar))) {
-    logmsg(ANDROID_LOG_FATAL, "%s config item needed", item_name);
-    return NULL;
-  }
-
-  errno    = 0;
-  conf_int = strtol(tmp, &endptr, 10);
-  if (errno > 0) {
-    logmsg(ANDROID_LOG_FATAL, "%s config item is not numeric: %s (error=%s)", item_name, tmp,
-           strerror(errno));
-    return NULL;
-  }
-  if (endptr == tmp || *tmp == '\0') {
-    logmsg(ANDROID_LOG_FATAL, "%s config item is not numeric: %s", item_name, tmp);
-    return NULL;
-  }
-  if (*endptr != '\0') {
-    logmsg(ANDROID_LOG_FATAL, "%s config item contains non-numeric characters: %s", item_name,
-           endptr);
-    return NULL;
-  }
-  if (conf_int > INT16_MAX || conf_int < INT16_MIN) {
-    logmsg(ANDROID_LOG_FATAL, "%s config item is too big/small: %d", item_name, conf_int);
-    return NULL;
-  }
-  *ret_val_ptr = conf_int;
-  return ret_val_ptr;
-}
-
 /* function: config_item_ip
  * locates the config item, parses the ipv4 address, and returns the pointer ret_val_ptr, or NULL on
  * failure
@@ -122,33 +62,6 @@
   return ret_val_ptr;
 }
 
-/* function: config_item_ip6
- * locates the config item, parses the ipv6 address, and returns the pointer ret_val_ptr, or NULL on
- * failure
- *   root        - parsed configuration
- *   item_name   - name of config item to locate
- *   defaultvar  - value to use if config item isn't present
- *   ret_val_ptr - pointer for return value storage
- */
-struct in6_addr *config_item_ip6(cnode *root, const char *item_name, const char *defaultvar,
-                                 struct in6_addr *ret_val_ptr) {
-  const char *tmp;
-  int status;
-
-  if (!(tmp = config_str(root, item_name, defaultvar))) {
-    logmsg(ANDROID_LOG_FATAL, "%s config item needed", item_name);
-    return NULL;
-  }
-
-  status = inet_pton(AF_INET6, tmp, ret_val_ptr);
-  if (status <= 0) {
-    logmsg(ANDROID_LOG_FATAL, "invalid IPv6 address specified for %s: %s", item_name, tmp);
-    return NULL;
-  }
-
-  return ret_val_ptr;
-}
-
 /* function: ipv6_prefix_equal
  * compares the prefixes two ipv6 addresses. assumes the prefix lengths are both /64.
  *   a1 - first address
@@ -157,107 +70,6 @@
  */
 int ipv6_prefix_equal(struct in6_addr *a1, struct in6_addr *a2) { return !memcmp(a1, a2, 8); }
 
-/* function: gen_random_iid
- * picks a random interface ID that is checksum neutral with the IPv4 address and the NAT64 prefix
- *   myaddr            - IPv6 address to write to
- *   ipv4_local_subnet - clat IPv4 address
- *   plat_subnet       - 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;
-}
-
-// Factored out to a separate function for testability.
-int connect_is_ipv4_address_free(in_addr_t addr) {
-  int s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
-  if (s == -1) {
-    return 0;
-  }
-
-  // Attempt to connect to the address. If the connection succeeds and getsockname returns the same
-  // the address then the address is already assigned to the system and we can't use it.
-  struct sockaddr_in sin = { .sin_family = AF_INET, .sin_addr = { addr }, .sin_port = htons(53) };
-  socklen_t len          = sizeof(sin);
-  int inuse              = connect(s, (struct sockaddr *)&sin, sizeof(sin)) == 0 &&
-              getsockname(s, (struct sockaddr *)&sin, &len) == 0 && (size_t)len >= sizeof(sin) &&
-              sin.sin_addr.s_addr == addr;
-
-  close(s);
-  return !inuse;
-}
-
-addr_free_func config_is_ipv4_address_free = connect_is_ipv4_address_free;
-
-/* function: config_select_ipv4_address
- * picks a free IPv4 address, starting from ip and trying all addresses in the prefix in order
- *   ip        - the IP address from the configuration file
- *   prefixlen - the length of the prefix from which addresses may be selected.
- *   returns: the IPv4 address, or INADDR_NONE if no addresses were available
- */
-in_addr_t config_select_ipv4_address(const struct in_addr *ip, int16_t prefixlen) {
-  in_addr_t chosen = INADDR_NONE;
-
-  // Don't accept prefixes that are too large because we scan addresses one by one.
-  if (prefixlen < 16 || prefixlen > 32) {
-    return chosen;
-  }
-
-  // All these are in host byte order.
-  in_addr_t mask       = 0xffffffff >> (32 - prefixlen) << (32 - prefixlen);
-  in_addr_t ipv4       = ntohl(ip->s_addr);
-  in_addr_t first_ipv4 = ipv4;
-  in_addr_t prefix     = ipv4 & mask;
-
-  // Pick the first IPv4 address in the pool, wrapping around if necessary.
-  // So, for example, 192.0.0.4 -> 192.0.0.5 -> 192.0.0.6 -> 192.0.0.7 -> 192.0.0.0.
-  do {
-    if (config_is_ipv4_address_free(htonl(ipv4))) {
-      chosen = htonl(ipv4);
-      break;
-    }
-    ipv4 = prefix | ((ipv4 + 1) & ~mask);
-  } while (ipv4 != first_ipv4);
-
-  return chosen;
-}
-
-/* function: config_generate_local_ipv6_subnet
- * generates the local ipv6 subnet when given the interface ip requires config.ipv6_host_id
- *   interface_ip - in: interface ip, out: local ipv6 host address
- */
-void config_generate_local_ipv6_subnet(struct in6_addr *interface_ip) {
-  int i;
-
-  if (Global_Clatd_Config.use_dynamic_iid) {
-    /* Generate a random interface ID. */
-    gen_random_iid(interface_ip, &Global_Clatd_Config.ipv4_local_subnet,
-                   &Global_Clatd_Config.plat_subnet);
-  } else {
-    /* Use the specified interface ID. */
-    for (i = 2; i < 4; i++) {
-      interface_ip->s6_addr32[i] = Global_Clatd_Config.ipv6_host_id.s6_addr32[i];
-    }
-  }
-}
-
 /* function: read_config
  * reads the config file and parses it into the global variable Global_Clatd_Config. returns 0 on
  * failure, 1 on success
@@ -266,7 +78,6 @@
  */
 int read_config(const char *file, const char *uplink_interface) {
   cnode *root   = config_node("", "");
-  unsigned flags;
 
   if (!root) {
     logmsg(ANDROID_LOG_FATAL, "out of memory");
@@ -288,22 +99,7 @@
                       &Global_Clatd_Config.ipv4_local_subnet))
     goto failed;
 
-  if (!config_item_int16_t(root, "ipv4_local_prefixlen", DEFAULT_IPV4_LOCAL_PREFIXLEN,
-                           &Global_Clatd_Config.ipv4_local_prefixlen))
-    goto failed;
-
-  if (!config_item_ip6(root, "ipv6_host_id", "::", &Global_Clatd_Config.ipv6_host_id)) goto failed;
-
-  /* In order to prevent multiple devices attempting to use the same clat address, never use a
-     statically-configured interface ID on a broadcast interface such as wifi. */
-  if (!IN6_IS_ADDR_UNSPECIFIED(&Global_Clatd_Config.ipv6_host_id)) {
-    ifc_init();
-    ifc_get_info(Global_Clatd_Config.default_pdp_interface, NULL, NULL, &flags);
-    ifc_close();
-    Global_Clatd_Config.use_dynamic_iid = (flags & IFF_BROADCAST) != 0;
-  } else {
-    Global_Clatd_Config.use_dynamic_iid = 1;
-  }
+  Global_Clatd_Config.ipv4_local_prefixlen = 29;
 
   return 1;
 
@@ -311,22 +107,3 @@
   free(root);
   return 0;
 }
-
-/* function; dump_config
- * prints the current config
- */
-void dump_config() {
-  char charbuffer[INET6_ADDRSTRLEN];
-
-  logmsg(
-    ANDROID_LOG_DEBUG, "ipv6_local_subnet = %s",
-    inet_ntop(AF_INET6, &Global_Clatd_Config.ipv6_local_subnet, charbuffer, sizeof(charbuffer)));
-  logmsg(
-    ANDROID_LOG_DEBUG, "ipv4_local_subnet = %s",
-    inet_ntop(AF_INET, &Global_Clatd_Config.ipv4_local_subnet, charbuffer, sizeof(charbuffer)));
-  logmsg(ANDROID_LOG_DEBUG, "ipv4_local_prefixlen = %d", Global_Clatd_Config.ipv4_local_prefixlen);
-  logmsg(ANDROID_LOG_DEBUG, "plat_subnet = %s",
-         inet_ntop(AF_INET6, &Global_Clatd_Config.plat_subnet, charbuffer, sizeof(charbuffer)));
-  logmsg(ANDROID_LOG_DEBUG, "default_pdp_interface = %s",
-         Global_Clatd_Config.default_pdp_interface);
-}
diff --git a/config.h b/config.h
index c47fc88..555b968 100644
--- a/config.h
+++ b/config.h
@@ -22,25 +22,18 @@
 #include <netinet/in.h>
 
 #define DEFAULT_IPV4_LOCAL_SUBNET "192.0.0.4"
-#define DEFAULT_IPV4_LOCAL_PREFIXLEN "29"
 
 struct clat_config {
   struct in6_addr ipv6_local_subnet;
-  struct in6_addr ipv6_host_id;
   struct in_addr ipv4_local_subnet;
   int16_t ipv4_local_prefixlen;
   struct in6_addr plat_subnet;
   char *default_pdp_interface;
-  int use_dynamic_iid;
 };
 
 extern struct clat_config Global_Clatd_Config;
 
 int read_config(const char *file, const char *uplink_interface);
-void config_generate_local_ipv6_subnet(struct in6_addr *interface_ip);
-in_addr_t config_select_ipv4_address(const struct in_addr *ip, int16_t prefixlen);
 int ipv6_prefix_equal(struct in6_addr *a1, struct in6_addr *a2);
 
-typedef int (*addr_free_func)(in_addr_t addr);
-
 #endif /* __CONFIG_H__ */