diff --git a/Android.mk b/Android.mk
index 635f2f6..e732c72 100644
--- a/Android.mk
+++ b/Android.mk
@@ -3,7 +3,6 @@
 
 LOCAL_SRC_FILES:=clatd.c dump.c checksum.c translate.c icmp.c ipv4.c ipv6.c config.c dns64.c logging.c getaddr.c getroute.c netlink_callbacks.c netlink_msg.c setif.c setroute.c mtu.c
 
-LOCAL_CFLAGS := -Wall -Werror
 LOCAL_C_INCLUDES := external/libnl/include
 LOCAL_STATIC_LIBRARIES := libnl
 LOCAL_SHARED_LIBRARIES := libcutils liblog
diff --git a/checksum.c b/checksum.c
index 099be6a..a4dc9b8 100644
--- a/checksum.c
+++ b/checksum.c
@@ -49,25 +49,17 @@
   return checksum;
 }
 
-/* function: ip_checksum_fold
- * folds a 32-bit partial checksum into 16 bits
+/* function: ip_checksum_finish
+ * close the checksum
  * temp_sum - sum from ip_checksum_add
- * returns: the folded checksum in network byte order
  */
-uint16_t ip_checksum_fold(uint32_t temp_sum) {
+uint16_t ip_checksum_finish(uint32_t temp_sum) {
   while(temp_sum > 0xffff)
     temp_sum = (temp_sum >> 16) + (temp_sum & 0xFFFF);
 
-  return temp_sum;
-}
+  temp_sum = (~temp_sum) & 0xffff;
 
-/* function: ip_checksum_finish
- * folds and closes the checksum
- * temp_sum - sum from ip_checksum_add
- * returns: a header checksum value in network byte order
- */
-uint16_t ip_checksum_finish(uint32_t temp_sum) {
-  return ~ip_checksum_fold(temp_sum);
+  return temp_sum;
 }
 
 /* function: ip_checksum
@@ -121,23 +113,3 @@
 
   return current;
 }
-
-/* function: ip_checksum_adjust
- * calculates a new checksum given a previous checksum and the old and new pseudo-header checksums
- * checksum    - the header checksum in the original packet in network byte order
- * old_hdr_sum - the pseudo-header checksum of the original packet
- * new_hdr_sum - the pseudo-header checksum of the translated packet
- * returns: the new header checksum in network byte order
- */
-uint16_t ip_checksum_adjust(uint16_t checksum, uint32_t old_hdr_sum, uint32_t new_hdr_sum) {
-  // Algorithm suggested in RFC 1624.
-  // http://tools.ietf.org/html/rfc1624#section-3
-  checksum = ~checksum;
-  uint16_t folded_sum = ip_checksum_fold(checksum + new_hdr_sum);
-  uint16_t folded_old = ip_checksum_fold(old_hdr_sum);
-  if (folded_sum > folded_old) {
-    return ~(folded_sum - folded_old);
-  } else {
-    return ~(folded_sum - folded_old - 1);  // end-around borrow
-  }
-}
diff --git a/checksum.h b/checksum.h
index 44921f0..473f5f5 100644
--- a/checksum.h
+++ b/checksum.h
@@ -25,6 +25,4 @@
 uint32_t ipv6_pseudo_header_checksum(uint32_t current, const struct ip6_hdr *ip6, uint16_t len);
 uint32_t ipv4_pseudo_header_checksum(uint32_t current, const struct iphdr *ip, uint16_t len);
 
-uint16_t ip_checksum_adjust(uint16_t checksum, uint32_t old_hdr_sum, uint32_t new_hdr_sum);
-
 #endif /* __CHECKSUM_H__ */
diff --git a/clatd.c b/clatd.c
index 3ab2371..26ecb57 100644
--- a/clatd.c
+++ b/clatd.c
@@ -29,6 +29,15 @@
 #include <arpa/inet.h>
 #include <fcntl.h>
 
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
+#include <netinet/udp.h>
+#include <netinet/tcp.h>
+#include <netinet/ip6.h>
+#include <netinet/icmp6.h>
+#include <linux/icmp.h>
+
 #include <sys/capability.h>
 #include <sys/uio.h>
 #include <linux/prctl.h>
@@ -38,6 +47,8 @@
 
 #include <private/android_filesystem_config.h>
 
+#include "ipv4.h"
+#include "ipv6.h"
 #include "translate.h"
 #include "clatd.h"
 #include "config.h"
@@ -54,6 +65,11 @@
 int forwarding_fd = -1;
 volatile sig_atomic_t running = 1;
 
+struct tun_data {
+  char device6[IFNAMSIZ], device4[IFNAMSIZ];
+  int fd6, fd4;
+};
+
 /* function: set_forwarding
  * enables/disables ipv6 forwarding
  */
@@ -68,7 +84,7 @@
 /* function: stop_loop
  * signal handler: stop the event loop
  */
-void stop_loop() {
+void stop_loop(int signal) {
   running = 0;
 }
 
@@ -130,6 +146,7 @@
  * tunnel - tun device data
  */
 void configure_tun_ipv6(const struct tun_data *tunnel) {
+  struct in6_addr local_nat64_prefix_6;
   int status;
 
   status = if_route(tunnel->device6, AF_INET6, &Global_Clatd_Config.ipv6_local_subnet,
@@ -291,6 +308,56 @@
   configure_tun_ip(tunnel);
 }
 
+/* function: packet_handler
+ * takes a tun header and a packet and sends it down the stack
+ * tunnel     - tun device data
+ * tun_header - tun header
+ * packet     - packet
+ * packetsize - size of packet
+ */
+void packet_handler(const struct tun_data *tunnel, struct tun_pi *tun_header, const char *packet,
+                    size_t packetsize) {
+  int fd;
+  int iov_len = 0;
+
+  // Allocate buffers for all packet headers.
+  struct tun_pi tun_targ;
+  char iphdr[sizeof(struct ip6_hdr)];
+  char transporthdr[MAX_TCP_HDR];
+  char icmp_iphdr[sizeof(struct ip6_hdr)];
+  char icmp_transporthdr[MAX_TCP_HDR];
+
+  // iovec of the packets we'll send. This gets passed down to the translation functions.
+  clat_packet out = {
+    { &tun_targ, sizeof(tun_targ) },  // Tunnel header.
+    { iphdr, 0 },                     // IP header.
+    { transporthdr, 0 },              // Transport layer header.
+    { icmp_iphdr, 0 },                // ICMP error inner IP header.
+    { icmp_transporthdr, 0 },         // ICMP error transport layer header.
+    { NULL, 0 },                      // Payload. No buffer, it's a pointer to the original payload.
+  };
+
+  if(tun_header->flags != 0) {
+    logmsg(ANDROID_LOG_WARN,"packet_handler: unexpected flags = %d", tun_header->flags);
+  }
+
+  if(ntohs(tun_header->proto) == ETH_P_IP) {
+    fd = tunnel->fd6;
+    fill_tun_header(&tun_targ, ETH_P_IPV6);
+    iov_len = ipv4_packet(out, CLAT_POS_IPHDR, packet, packetsize);
+  } else if(ntohs(tun_header->proto) == ETH_P_IPV6) {
+    fd = tunnel->fd4;
+    fill_tun_header(&tun_targ, ETH_P_IP);
+    iov_len = ipv6_packet(out, CLAT_POS_IPHDR, packet, packetsize);
+  } else {
+    logmsg(ANDROID_LOG_WARN,"packet_handler: unknown packet type = %x",tun_header->proto);
+  }
+
+  if (iov_len > 0) {
+    writev(fd, out, iov_len);
+  }
+}
+
 /* function: read_packet
  * reads a packet from the tunnel fd and passes it down the stack
  * active_fd - tun file descriptor marked ready for reading
@@ -312,6 +379,7 @@
     logmsg(ANDROID_LOG_WARN,"read_packet/tun interface removed");
     running = 0;
   } else {
+    struct tun_pi tun_header;
     ssize_t header_size = sizeof(struct tun_pi);
 
     if(readlen < header_size) {
@@ -319,7 +387,7 @@
       return;
     }
 
-    translate_packet(tunnel, (struct tun_pi *) packet, packet + header_size, readlen - header_size);
+    packet_handler(tunnel, (struct tun_pi *) packet, packet + header_size, readlen - header_size);
   }
 }
 
diff --git a/clatd.h b/clatd.h
index 44a655e..3459b09 100644
--- a/clatd.h
+++ b/clatd.h
@@ -18,7 +18,6 @@
 #ifndef __CLATD_H__
 #define __CLATD_H__
 
-#include <linux/if.h>
 #include <linux/if_tun.h>
 
 #define MAXMTU 1500
@@ -31,9 +30,4 @@
 // how frequently (in seconds) to poll for an address change while there is no traffic
 #define NO_TRAFFIC_INTERFACE_POLL_FREQUENCY 90
 
-struct tun_data {
-  char device6[IFNAMSIZ], device4[IFNAMSIZ];
-  int fd6, fd4;
-};
-
 #endif /* __CLATD_H__ */
diff --git a/config.c b/config.c
index b82ac6c..61a4ebb 100644
--- a/config.c
+++ b/config.c
@@ -154,7 +154,7 @@
  * does dns lookups to set the plat subnet or exits on failure, waits forever for a dns response with a query backoff timer
  */
 void dns64_detection() {
-  int backoff_sleep, status;
+  int i, backoff_sleep, status;
   struct in6_addr tmp_ptr;
 
   backoff_sleep = 1;
diff --git a/icmp.c b/icmp.c
index 75a4a4d..af96b83 100644
--- a/icmp.c
+++ b/icmp.c
@@ -139,7 +139,7 @@
   }
 
   // We don't understand this ICMP type. Return parameter problem so the caller will bail out.
-  logmsg_dbg(ANDROID_LOG_DEBUG, "icmp6_to_icmp_type: unhandled ICMP type/code %d/%d", type, code);
+  logmsg_dbg(ANDROID_LOG_DEBUG, "icmp6_to_icmp_type: unhandled ICMP type %d", type);
   return ICMP_PARAMETERPROB;
 }
 
diff --git a/ipv4.c b/ipv4.c
index c828ffa..89e47e4 100644
--- a/ipv4.c
+++ b/ipv4.c
@@ -17,8 +17,18 @@
  */
 #include <string.h>
 
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
+#include <netinet/udp.h>
+#include <netinet/tcp.h>
+#include <netinet/ip6.h>
+#include <netinet/icmp6.h>
+#include <linux/icmp.h>
+
 #include "translate.h"
 #include "checksum.h"
+#include "ipv4.h"
 #include "logging.h"
 #include "debug.h"
 #include "dump.h"
@@ -61,7 +71,7 @@
   uint8_t nxthdr;
   const char *next_header;
   size_t len_left;
-  uint32_t old_sum, new_sum;
+  uint32_t checksum;
   int iov_len;
 
   if(len < sizeof(struct iphdr)) {
@@ -112,19 +122,14 @@
   out[pos].iov_len = sizeof(struct ip6_hdr);
 
   // Calculate the pseudo-header checksum.
-  old_sum = ipv4_pseudo_header_checksum(0, header, len_left);
-  new_sum = ipv6_pseudo_header_checksum(0, ip6_targ, len_left);
+  checksum = ipv6_pseudo_header_checksum(0, ip6_targ, len_left);
 
-  if (nxthdr == IPPROTO_ICMPV6) {
-    iov_len = icmp_packet(out, pos + 1, (const struct icmphdr *) next_header, new_sum, len_left);
-  } else if (nxthdr == IPPROTO_TCP) {
-    iov_len = tcp_packet(out, pos + 1, (const struct tcphdr *) next_header, old_sum, new_sum,
-                         len_left);
-  } else if (nxthdr == IPPROTO_UDP) {
-    iov_len = udp_packet(out, pos + 1, (const struct udphdr *) next_header, old_sum, new_sum,
-                         len_left);
-  } else if (nxthdr == IPPROTO_GRE) {
-    iov_len = generic_packet(out, pos + 1, next_header, len_left);
+  if(nxthdr == IPPROTO_ICMPV6) {
+    iov_len = icmp_packet(out, pos + 1, (const struct icmphdr *) next_header, checksum, len_left);
+  } else if(nxthdr == IPPROTO_TCP) {
+    iov_len = tcp_packet(out, pos + 1, (const struct tcphdr *) next_header, checksum, len_left);
+  } else if(nxthdr == IPPROTO_UDP) {
+    iov_len = udp_packet(out, pos + 1, (const struct udphdr *) next_header, checksum, len_left);
   } else {
 #if CLAT_DEBUG
     logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/unknown protocol: %x",header->protocol);
diff --git a/ipv4.h b/ipv4.h
new file mode 100644
index 0000000..00befd2
--- /dev/null
+++ b/ipv4.h
@@ -0,0 +1,25 @@
+/*
+ * Copyright 2011 Daniel Drown
+ *
+ * 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.
+ *
+ * ipv4.h - takes an ipv4 packet and hands it off to the proper translate function
+ */
+#ifndef __IPV4_H__
+#define __IPV4_H__
+
+#include "translate.h"
+
+int ipv4_packet(clat_packet out, int pos, const char *packet, size_t len);
+
+#endif /* __IPV4_H__ */
diff --git a/ipv6.c b/ipv6.c
index 371d9e1..ef1e62f 100644
--- a/ipv6.c
+++ b/ipv6.c
@@ -17,10 +17,19 @@
  */
 #include <string.h>
 
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
+#include <netinet/udp.h>
+#include <netinet/tcp.h>
+#include <netinet/ip6.h>
+#include <netinet/icmp6.h>
+#include <linux/icmp.h>
 #include <arpa/inet.h>
 
 #include "translate.h"
 #include "checksum.h"
+#include "ipv6.h"
 #include "logging.h"
 #include "dump.h"
 #include "config.h"
@@ -34,7 +43,8 @@
  * len      - size of ip payload
  * returns: the highest position in the output clat_packet that's filled in
  */
-int icmp6_packet(clat_packet out, int pos, const struct icmp6_hdr *icmp6, size_t len) {
+int icmp6_packet(clat_packet out, int pos, const struct icmp6_hdr *icmp6, uint32_t checksum,
+                 size_t len) {
   const char *payload;
   size_t payload_size;
 
@@ -46,7 +56,7 @@
   payload = (const char *) (icmp6 + 1);
   payload_size = len - sizeof(struct icmp6_hdr);
 
-  return icmp6_to_icmp(out, pos, icmp6, payload, payload_size);
+  return icmp6_to_icmp(out, pos, icmp6, checksum, payload, payload_size);
 }
 
 /* function: log_bad_address
@@ -54,18 +64,16 @@
  * fmt     - printf-style format, use %s to place the address
  * badaddr - the bad address in question
  */
-#if CLAT_DEBUG
 void log_bad_address(const char *fmt, const struct in6_addr *src, const struct in6_addr *dst) {
+#if CLAT_DEBUG
   char srcstr[INET6_ADDRSTRLEN];
   char dststr[INET6_ADDRSTRLEN];
 
   inet_ntop(AF_INET6, src, srcstr, sizeof(srcstr));
   inet_ntop(AF_INET6, dst, dststr, sizeof(dststr));
   logmsg_dbg(ANDROID_LOG_ERROR, fmt, srcstr, dststr);
-}
-#else
-#define log_bad_address(fmt, src, dst)
 #endif
+}
 
 /* function: ipv6_packet
  * takes an ipv6 packet and hands it off to the layer 4 protocol function
@@ -80,8 +88,9 @@
   uint8_t protocol;
   const char *next_header;
   size_t len_left;
-  uint32_t old_sum, new_sum;
+  uint32_t checksum;
   int iov_len;
+  int i;
 
   if(len < sizeof(struct ip6_hdr)) {
     logmsg_dbg(ANDROID_LOG_ERROR, "ipv6_packet/too short for an ip6 header: %d", len);
@@ -125,20 +134,18 @@
   out[pos].iov_len = sizeof(struct iphdr);
 
   // Calculate the pseudo-header checksum.
-  old_sum = ipv6_pseudo_header_checksum(0, ip6, len_left);
-  new_sum = ipv4_pseudo_header_checksum(0, ip_targ, len_left);
+  checksum = ipv4_pseudo_header_checksum(0, ip_targ, len_left);
 
   // does not support IPv6 extension headers, this will drop any packet with them
-  if (protocol == IPPROTO_ICMP) {
-    iov_len = icmp6_packet(out, pos + 1, (const struct icmp6_hdr *) next_header, len_left);
-  } else if (ip6->ip6_nxt == IPPROTO_TCP) {
-    iov_len = tcp_packet(out, pos + 1, (const struct tcphdr *) next_header, old_sum, new_sum,
+  if(protocol == IPPROTO_ICMP) {
+    iov_len = icmp6_packet(out, pos + 1, (const struct icmp6_hdr *) next_header, checksum,
+                           len_left);
+  } else if(ip6->ip6_nxt == IPPROTO_TCP) {
+    iov_len = tcp_packet(out, pos + 1, (const struct tcphdr *) next_header, checksum,
                          len_left);
-  } else if (ip6->ip6_nxt == IPPROTO_UDP) {
-    iov_len = udp_packet(out, pos + 1, (const struct udphdr *) next_header, old_sum, new_sum,
+  } else if(ip6->ip6_nxt == IPPROTO_UDP) {
+    iov_len = udp_packet(out, pos + 1, (const struct udphdr *) next_header, checksum,
                          len_left);
-  } else if (ip6->ip6_nxt == IPPROTO_GRE) {
-    iov_len = generic_packet(out, pos + 1, next_header, len_left);
   } else {
 #if CLAT_DEBUG
     logmsg(ANDROID_LOG_ERROR, "ipv6_packet/unknown next header type: %x", ip6->ip6_nxt);
diff --git a/ipv6.h b/ipv6.h
new file mode 100644
index 0000000..019de17
--- /dev/null
+++ b/ipv6.h
@@ -0,0 +1,25 @@
+/*
+ * Copyright 2011 Daniel Drown
+ *
+ * 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.
+ *
+ * ipv6.h - takes an ipv6 packet and hands it off to the proper translate function
+ */
+#ifndef __IPV6_H__
+#define __IPV6_H__
+
+#include "translate.h"
+
+int ipv6_packet(clat_packet out, int pos, const char *packet, size_t len);
+
+#endif /* __IPV6_H__ */
diff --git a/translate.c b/translate.c
index f7f09cb..fc70f3d 100644
--- a/translate.c
+++ b/translate.c
@@ -16,7 +16,15 @@
  * translate.c - CLAT functions / partial implementation of rfc6145
  */
 #include <string.h>
-#include <sys/uio.h>
+
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
+#include <netinet/udp.h>
+#include <netinet/tcp.h>
+#include <netinet/ip6.h>
+#include <netinet/icmp6.h>
+#include <linux/icmp.h>
 
 #include "icmp.h"
 #include "translate.h"
@@ -141,7 +149,7 @@
   // Third-party ICMPv6 message. This may have been originated by an native IPv6 address.
   // In that case, the source IPv6 address can't be translated and we need to make up an IPv4
   // source address. For now, use 255.0.0.<ttl>, which at least looks useful in traceroute.
-  if ((uint32_t) ip->saddr == INADDR_NONE) {
+  if (ip->saddr == (uint32_t) INADDR_NONE) {
     ttl_guess = icmp_guess_ttl(old_header->ip6_hlim);
     ip->saddr = htonl((0xff << 24) + ttl_guess);
   }
@@ -167,7 +175,6 @@
   ip6->ip6_dst = ipv4_addr_to_ipv6_addr(old_header->daddr);
 }
 
-
 /* function: icmp_to_icmp6
  * translate ipv4 icmp to ipv6 icmp
  * out          - output packet
@@ -201,10 +208,12 @@
     // The pseudo-header checksum was calculated on the transport length of the original IPv4
     // packet that we were asked to translate. This transport length is 20 bytes smaller than it
     // needs to be, because the ICMP error contains an IPv4 header, which we will be translating to
-    // an IPv6 header, which is 20 bytes longer. Fix it up here.
+    // an IPv6 header, which is 20 bytes longer. Fix it up here. This is simpler than the
+    // alternative, which is to always update the pseudo-header checksum in all UDP/TCP/ICMP
+    // translation functions (rather than pre-calculating it when translating the IPv4 header).
     // We only need to do this for ICMP->ICMPv6, not ICMPv6->ICMP, because ICMP does not use the
     // pseudo-header when calculating its checksum (as the IPv4 header has its own checksum).
-    checksum = checksum + htons(20);
+    checksum = htonl(ntohl(checksum) + 20);
   } else if (icmp6_type == ICMP6_ECHO_REQUEST || icmp6_type == ICMP6_ECHO_REPLY) {
     // Ping packet.
     icmp6_targ->icmp6_id = icmp->un.echo.id;
@@ -227,14 +236,16 @@
  * translate ipv6 icmp to ipv4 icmp
  * out          - output packet
  * icmp6        - source packet icmp6 header
+ * checksum     - pseudo-header checksum (unused)
  * payload      - icmp6 payload
  * payload_size - size of payload
  * returns: the highest position in the output clat_packet that's filled in
  */
-int icmp6_to_icmp(clat_packet out, int pos, const struct icmp6_hdr *icmp6,
+int icmp6_to_icmp(clat_packet out, int pos, const struct icmp6_hdr *icmp6, uint32_t checksum,
                   const char *payload, size_t payload_size) {
   struct icmphdr *icmp_targ = out[pos].iov_base;
   uint8_t icmp_type;
+  int ttl;
   int clat_packet_len;
 
   memset(icmp_targ, 0, sizeof(struct icmphdr));
@@ -269,32 +280,14 @@
   return clat_packet_len;
 }
 
-/* function: generic_packet
- * takes a generic IP packet and sets it up for translation
- * out      - output packet
- * pos      - position in the output packet of the transport header
- * payload  - pointer to IP payload
- * len      - size of ip payload
- * returns: the highest position in the output clat_packet that's filled in
- */
-int generic_packet(clat_packet out, int pos, const char *payload, size_t len) {
-  out[pos].iov_len = 0;
-  out[CLAT_POS_PAYLOAD].iov_base = (char *) payload;
-  out[CLAT_POS_PAYLOAD].iov_len = len;
-
-  return CLAT_POS_PAYLOAD + 1;
-}
-
 /* function: udp_packet
  * takes a udp packet and sets it up for translation
  * out      - output packet
  * udp      - pointer to udp header in packet
- * old_sum  - pseudo-header checksum of old header
- * new_sum  - pseudo-header checksum of new header
+ * checksum - pseudo-header checksum
  * len      - size of ip payload
  */
-int udp_packet(clat_packet out, int pos, const struct udphdr *udp,
-               uint32_t old_sum, uint32_t new_sum, size_t len) {
+int udp_packet(clat_packet out, int pos, const struct udphdr *udp, uint32_t checksum, size_t len) {
   const char *payload;
   size_t payload_size;
 
@@ -306,7 +299,7 @@
   payload = (const char *) (udp + 1);
   payload_size = len - sizeof(struct udphdr);
 
-  return udp_translate(out, pos, udp, old_sum, new_sum, payload, payload_size);
+  return udp_translate(out, pos, udp, checksum, payload, payload_size);
 }
 
 /* function: tcp_packet
@@ -317,8 +310,7 @@
  * len      - size of ip payload
  * returns: the highest position in the output clat_packet that's filled in
  */
-int tcp_packet(clat_packet out, int pos, const struct tcphdr *tcp,
-               uint32_t old_sum, uint32_t new_sum, size_t len) {
+int tcp_packet(clat_packet out, int pos, const struct tcphdr *tcp, uint32_t checksum, size_t len) {
   const char *payload;
   size_t payload_size, header_size;
 
@@ -341,21 +333,20 @@
   payload = ((const char *) tcp) + header_size;
   payload_size = len - header_size;
 
-  return tcp_translate(out, pos, tcp, header_size, old_sum, new_sum, payload, payload_size);
+  return tcp_translate(out, pos, tcp, header_size, checksum, payload, payload_size);
 }
 
 /* function: udp_translate
  * common between ipv4/ipv6 - setup checksum and send udp packet
  * out          - output packet
  * udp          - udp header
- * old_sum      - pseudo-header checksum of old header
- * new_sum      - pseudo-header checksum of new header
+ * checksum     - pseudo-header checksum
  * payload      - tcp payload
  * payload_size - size of payload
  * returns: the highest position in the output clat_packet that's filled in
  */
-int udp_translate(clat_packet out, int pos, const struct udphdr *udp, uint32_t old_sum,
-                  uint32_t new_sum, const char *payload, size_t payload_size) {
+int udp_translate(clat_packet out, int pos, const struct udphdr *udp, uint32_t checksum,
+                  const char *payload, size_t payload_size) {
   struct udphdr *udp_targ = out[pos].iov_base;
 
   memcpy(udp_targ, udp, sizeof(struct udphdr));
@@ -364,22 +355,8 @@
   out[CLAT_POS_PAYLOAD].iov_base = (char *) payload;
   out[CLAT_POS_PAYLOAD].iov_len = payload_size;
 
-  if (udp_targ->check) {
-    udp_targ->check = ip_checksum_adjust(udp->check, old_sum, new_sum);
-  } else {
-    // Zero checksums are special. RFC 768 says, "An all zero transmitted checksum value means that
-    // the transmitter generated no checksum (for debugging or for higher level protocols that
-    // don't care)." However, in IPv6 zero UDP checksums were only permitted by RFC 6935 (2013). So
-    // for safety we recompute it.
-    udp_targ->check = 0;  // Checksum field must be 0 when calculating checksum.
-    udp_targ->check = packet_checksum(new_sum, out, pos);
-  }
-
-  // RFC 768: "If the computed checksum is zero, it is transmitted as all ones (the equivalent
-  // in one's complement arithmetic)."
-  if (!udp_targ->check) {
-    udp_targ->check = 0xffff;
-  }
+  udp_targ->check = 0;  // Checksum field must be 0 when calculating checksum.
+  udp_targ->check = packet_checksum(checksum, out, pos);
 
   return CLAT_POS_PAYLOAD + 1;
 }
@@ -398,7 +375,7 @@
  * TODO: hosts without pmtu discovery - non DF packets will rely on fragmentation (unimplemented)
  */
 int tcp_translate(clat_packet out, int pos, const struct tcphdr *tcp, size_t header_size,
-                  uint32_t old_sum, uint32_t new_sum, const char *payload, size_t payload_size) {
+                  uint32_t checksum, const char *payload, size_t payload_size) {
   struct tcphdr *tcp_targ = out[pos].iov_base;
   out[pos].iov_len = header_size;
 
@@ -415,57 +392,8 @@
   out[CLAT_POS_PAYLOAD].iov_base = (char *)payload;
   out[CLAT_POS_PAYLOAD].iov_len = payload_size;
 
-  tcp_targ->check = ip_checksum_adjust(tcp->check, old_sum, new_sum);
+  tcp_targ->check = 0;  // Checksum field must be 0 when calculating checksum.
+  tcp_targ->check = packet_checksum(checksum, out, pos);
 
   return CLAT_POS_PAYLOAD + 1;
 }
-
-/* function: translate_packet
- * takes a tun header and a packet and sends it down the stack
- * tunnel     - tun device data
- * tun_header - tun header
- * packet     - packet
- * packetsize - size of packet
- */
-void translate_packet(const struct tun_data *tunnel, struct tun_pi *tun_header, const char *packet,
-                      size_t packetsize) {
-  int fd;
-  int iov_len = 0;
-
-  // Allocate buffers for all packet headers.
-  struct tun_pi tun_targ;
-  char iphdr[sizeof(struct ip6_hdr)];
-  char transporthdr[MAX_TCP_HDR];
-  char icmp_iphdr[sizeof(struct ip6_hdr)];
-  char icmp_transporthdr[MAX_TCP_HDR];
-
-  // iovec of the packets we'll send. This gets passed down to the translation functions.
-  clat_packet out = {
-    { &tun_targ, sizeof(tun_targ) },  // Tunnel header.
-    { iphdr, 0 },                     // IP header.
-    { transporthdr, 0 },              // Transport layer header.
-    { icmp_iphdr, 0 },                // ICMP error inner IP header.
-    { icmp_transporthdr, 0 },         // ICMP error transport layer header.
-    { NULL, 0 },                      // Payload. No buffer, it's a pointer to the original payload.
-  };
-
-  if(tun_header->flags != 0) {
-    logmsg(ANDROID_LOG_WARN, "translate_packet: unexpected flags = %d", tun_header->flags);
-  }
-
-  if(ntohs(tun_header->proto) == ETH_P_IP) {
-    fd = tunnel->fd6;
-    fill_tun_header(&tun_targ, ETH_P_IPV6);
-    iov_len = ipv4_packet(out, CLAT_POS_IPHDR, packet, packetsize);
-  } else if(ntohs(tun_header->proto) == ETH_P_IPV6) {
-    fd = tunnel->fd4;
-    fill_tun_header(&tun_targ, ETH_P_IP);
-    iov_len = ipv6_packet(out, CLAT_POS_IPHDR, packet, packetsize);
-  } else {
-    logmsg(ANDROID_LOG_WARN, "translate_packet: unknown packet type = %x",tun_header->proto);
-  }
-
-  if (iov_len > 0) {
-    writev(fd, out, iov_len);
-  }
-}
diff --git a/translate.h b/translate.h
index 3378254..fded251 100644
--- a/translate.h
+++ b/translate.h
@@ -18,18 +18,8 @@
 #ifndef __TRANSLATE_H__
 #define __TRANSLATE_H__
 
-#include <netinet/in.h>
-#include <netinet/ip.h>
-#include <netinet/ip_icmp.h>
-#include <netinet/udp.h>
-#include <netinet/tcp.h>
-#include <netinet/ip6.h>
-#include <netinet/icmp6.h>
-#include <linux/icmp.h>
 #include <linux/if_tun.h>
 
-#include "clatd.h"
-
 #define MAX_TCP_HDR (15 * 4)   // Data offset field is 4 bits and counts in 32-bit words.
 
 // A clat_packet is an array of iovec structures representing a packet that we are translating.
@@ -57,32 +47,19 @@
 void fill_ip6_header(struct ip6_hdr *ip6, uint16_t payload_len, uint8_t protocol,
                      const struct iphdr *old_header);
 
-// Translate and send packets.
-void translate_packet(const struct tun_data *tunnel, struct tun_pi *tun_header, const char *packet,
-                      size_t packetsize);
-
-// Translate IPv4 and IPv6 packets.
-int ipv4_packet(clat_packet out, int pos, const char *packet, size_t len);
-int ipv6_packet(clat_packet out, int pos, const char *packet, size_t len);
-
 // Translate ICMP packets.
 int icmp_to_icmp6(clat_packet out, int pos, const struct icmphdr *icmp, uint32_t checksum,
                   const char *payload, size_t payload_size);
-int icmp6_to_icmp(clat_packet out, int pos, const struct icmp6_hdr *icmp6,
+int icmp6_to_icmp(clat_packet out, int pos, const struct icmp6_hdr *icmp6, uint32_t checksum,
                   const char *payload, size_t payload_size);
 
-// Translate generic IP packets.
-int generic_packet(clat_packet out, int pos, const char *payload, size_t len);
-
 // Translate TCP and UDP packets.
-int tcp_packet(clat_packet out, int pos, const struct tcphdr *tcp,
-               uint32_t old_sum, uint32_t new_sum, size_t len);
-int udp_packet(clat_packet out, int pos, const struct udphdr *udp,
-               uint32_t old_sum, uint32_t new_sum, size_t len);
+int tcp_packet(clat_packet out, int pos, const struct tcphdr *tcp, uint32_t checksum, size_t len);
+int udp_packet(clat_packet out, int pos, const struct udphdr *udp, uint32_t checksum, size_t len);
 
 int tcp_translate(clat_packet out, int pos, const struct tcphdr *tcp, size_t header_size,
-                  uint32_t old_sum, uint32_t new_sum, const char *payload, size_t payload_size);
-int udp_translate(clat_packet out, int pos, const struct udphdr *udp,
-                  uint32_t old_sum, uint32_t new_sum, const char *payload, size_t payload_size);
+                  uint32_t checksum, const char *payload, size_t payload_size);
+int udp_translate(clat_packet out, int pos, const struct udphdr *udp, uint32_t checksum,
+                  const char *payload, size_t payload_size);
 
 #endif /* __TRANSLATE_H__ */