Derive mtu from ipv6 route to ipv4 /96 prefix instead of device
Test: builds, atest, still needs testing on real network
x86 clatd_test
--------------
clatd_test (19 Tests)
...
[6/19] ClatdTest#DetectMtu: PASSED (0ms)
...
Bug: 147935930
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I3d11ba082dabf70089867146acd84f6436953663
diff --git a/Android.bp b/Android.bp
index 42fbdaa..ae4bf1d 100644
--- a/Android.bp
+++ b/Android.bp
@@ -30,7 +30,6 @@
"ipv4.c",
"ipv6.c",
"logging.c",
- "mtu.c",
"netlink_callbacks.c",
"netlink_msg.c",
"ring.c",
diff --git a/clatd.c b/clatd.c
index 8a0d55f..82df63d 100644
--- a/clatd.c
+++ b/clatd.c
@@ -46,7 +46,6 @@
#include "dump.h"
#include "getaddr.h"
#include "logging.h"
-#include "mtu.h"
#include "resolv_netid.h"
#include "ring.h"
#include "setif.h"
@@ -149,8 +148,9 @@
/* 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) {
+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 {
@@ -170,7 +170,7 @@
exit(1);
}
- status = if_up(tunnel->device4, Global_Clatd_Config.ipv4mtu);
+ status = if_up(tunnel->device4, mtu);
if (status < 0) {
logmsg(ANDROID_LOG_FATAL, "configure_tun_ip/if_up(4) failed: %s", strerror(-status));
exit(1);
@@ -346,41 +346,74 @@
return 1;
}
+int detect_mtu(const struct in6_addr *plat_subnet, uint32_t plat_suffix, uint32_t mark) {
+ // Create an IPv6 UDP socket.
+ int s = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, 0);
+ if (s < 0) {
+ logmsg(ANDROID_LOG_FATAL, "socket(AF_INET6, SOCK_DGRAM, 0) failed");
+ exit(1);
+ }
+
+ // Socket's mark affects routing decisions (network selection)
+ if ((mark != MARK_UNSET) && setsockopt(s, SOL_SOCKET, SO_MARK, &mark, sizeof(mark))) {
+ logmsg(ANDROID_LOG_FATAL, "setsockopt(SOL_SOCKET, SO_MARK) failed: %s", strerror(errno));
+ exit(1);
+ }
+
+ // Try to connect udp socket to plat_subnet(96 bits):plat_suffix(32 bits)
+ struct sockaddr_in6 dst = {
+ .sin6_family = AF_INET6,
+ .sin6_addr = *plat_subnet,
+ };
+ dst.sin6_addr.s6_addr32[3] = plat_suffix;
+ if (connect(s, (struct sockaddr *)&dst, sizeof(dst))) {
+ logmsg(ANDROID_LOG_FATAL, "connect() failed: %s", strerror(errno));
+ exit(1);
+ }
+
+ // Fetch the socket's IPv6 mtu - this is effectively fetching mtu from routing table
+ int mtu;
+ socklen_t sz_mtu = sizeof(mtu);
+ if (getsockopt(s, SOL_IPV6, IPV6_MTU, &mtu, &sz_mtu)) {
+ logmsg(ANDROID_LOG_FATAL, "getsockopt(SOL_IPV6, IPV6_MTU) failed: %s", strerror(errno));
+ exit(1);
+ }
+ if (sz_mtu != sizeof(mtu)) {
+ logmsg(ANDROID_LOG_FATAL, "getsockopt(SOL_IPV6, IPV6_MTU) returned unexpected size: %d",
+ sz_mtu);
+ exit(1);
+ }
+ close(s);
+
+ return mtu;
+}
+
/* function: configure_interface
* reads the configuration and applies it to the interface
* uplink_interface - network interface to use to reach the ipv6 internet
* plat_prefix - PLAT prefix to use
* tunnel - tun device data
* net_id - NetID to use, NETID_UNSET indicates use of default network
+ * mark - the socket mark to use for the sending raw socket
*/
void configure_interface(const char *uplink_interface, const char *plat_prefix, const char *v4_addr,
- const char *v6_addr, struct tun_data *tunnel, unsigned net_id) {
-
+ const char *v6_addr, struct tun_data *tunnel, unsigned net_id,
+ uint32_t mark) {
if (!read_config("/system/etc/clatd.conf", uplink_interface, plat_prefix, net_id)) {
logmsg(ANDROID_LOG_FATAL, "read_config failed");
exit(1);
}
- if (Global_Clatd_Config.mtu > MAXMTU) {
- logmsg(ANDROID_LOG_WARN, "Max MTU is %d, requested %d", MAXMTU, Global_Clatd_Config.mtu);
- Global_Clatd_Config.mtu = MAXMTU;
- }
- if (Global_Clatd_Config.mtu <= 0) {
- Global_Clatd_Config.mtu = getifmtu(Global_Clatd_Config.default_pdp_interface);
- logmsg(ANDROID_LOG_WARN, "ifmtu=%d", Global_Clatd_Config.mtu);
- }
- if (Global_Clatd_Config.mtu < 1280) {
- logmsg(ANDROID_LOG_WARN, "mtu too small = %d", Global_Clatd_Config.mtu);
- Global_Clatd_Config.mtu = 1280;
- }
+ int mtu = detect_mtu(&Global_Clatd_Config.plat_subnet, htonl(0x08080808), mark);
+ // clamp to minimum ipv6 mtu - this probably cannot ever trigger
+ if (mtu < 1280) mtu = 1280;
+ // clamp to buffer size
+ if (mtu > MAXMTU) mtu = MAXMTU;
+ // decrease by ipv6(40) + ipv6 fragmentation header(8) vs ipv4(20) overhead of 28 bytes
+ mtu -= MTU_DELTA;
+ logmsg(ANDROID_LOG_WARN, "ipv4 mtu is %d", mtu);
- if (Global_Clatd_Config.ipv4mtu <= 0 ||
- Global_Clatd_Config.ipv4mtu > Global_Clatd_Config.mtu - MTU_DELTA) {
- Global_Clatd_Config.ipv4mtu = Global_Clatd_Config.mtu - MTU_DELTA;
- logmsg(ANDROID_LOG_WARN, "ipv4mtu now set to = %d", Global_Clatd_Config.ipv4mtu);
- }
-
- configure_tun_ip(tunnel, v4_addr);
+ configure_tun_ip(tunnel, v4_addr, mtu);
if (!configure_clat_ipv6_address(tunnel, uplink_interface, v6_addr)) {
exit(1);
diff --git a/clatd.h b/clatd.h
index d3869bf..e1d28a7 100644
--- a/clatd.h
+++ b/clatd.h
@@ -36,15 +36,16 @@
#define NO_TRAFFIC_INTERFACE_POLL_FREQUENCY 90
void stop_loop();
-void configure_tun_ip(const struct tun_data *tunnel, const char *v4_addr);
+void configure_tun_ip(const struct tun_data *tunnel, const char *v4_addr, int mtu);
void set_capability(uint64_t target_cap);
void drop_root_but_keep_caps();
void open_sockets(struct tun_data *tunnel, uint32_t mark);
int ipv6_address_changed(const char *interface);
int configure_clat_ipv6_address(const struct tun_data *tunnel, const char *interface,
const char *src_addr);
+int detect_mtu(const struct in6_addr *plat_subnet, uint32_t plat_suffix, uint32_t mark);
void configure_interface(const char *uplink_interface, const char *plat_prefix, const char *v4_addr,
- const char *v6, struct tun_data *tunnel, unsigned net_id);
+ const char *v6, struct tun_data *tunnel, unsigned net_id, uint32_t mark);
void event_loop(struct tun_data *tunnel);
/* function: parse_int
diff --git a/clatd_test.cpp b/clatd_test.cpp
index f01f49d..08b444c 100644
--- a/clatd_test.cpp
+++ b/clatd_test.cpp
@@ -772,12 +772,16 @@
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;
- Global_Clatd_Config.ipv4mtu = 1472;
// Create an interface for configure_tun_ip to configure and bring up.
TunInterface v4Iface;
@@ -785,7 +789,7 @@
struct tun_data tunnel = makeTunData();
strlcpy(tunnel.device4, v4Iface.name().c_str(), sizeof(tunnel.device4));
- configure_tun_ip(&tunnel, nullptr /* v4_addr */);
+ 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);
@@ -801,7 +805,6 @@
config_is_ipv4_address_free = over6_free;
Global_Clatd_Config.ipv4_local_prefixlen = 29;
- Global_Clatd_Config.ipv4mtu = 1472;
// Create an interface for configure_tun_ip to configure and bring up.
TunInterface v4Iface;
@@ -809,7 +812,7 @@
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 */);
+ 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);
diff --git a/config.c b/config.c
index 3ea510d..1c1a1f7 100644
--- a/config.c
+++ b/config.c
@@ -318,10 +318,6 @@
Global_Clatd_Config.default_pdp_interface = strdup(uplink_interface);
if (!Global_Clatd_Config.default_pdp_interface) goto failed;
- Global_Clatd_Config.mtu = -1;
-
- Global_Clatd_Config.ipv4mtu = -1;
-
if (!config_item_ip(root, "ipv4_local_subnet", DEFAULT_IPV4_LOCAL_SUBNET,
&Global_Clatd_Config.ipv4_local_subnet))
goto failed;
@@ -377,8 +373,6 @@
void dump_config() {
char charbuffer[INET6_ADDRSTRLEN];
- logmsg(ANDROID_LOG_DEBUG, "mtu = %d", Global_Clatd_Config.mtu);
- logmsg(ANDROID_LOG_DEBUG, "ipv4mtu = %d", Global_Clatd_Config.ipv4mtu);
logmsg(
ANDROID_LOG_DEBUG, "ipv6_local_subnet = %s",
inet_ntop(AF_INET6, &Global_Clatd_Config.ipv6_local_subnet, charbuffer, sizeof(charbuffer)));
diff --git a/config.h b/config.h
index 88c632a..d5c4399 100644
--- a/config.h
+++ b/config.h
@@ -26,7 +26,6 @@
#define DNS64_DETECTION_HOSTNAME "ipv4only.arpa"
struct clat_config {
- int16_t mtu, ipv4mtu;
struct in6_addr ipv6_local_subnet;
struct in6_addr ipv6_host_id;
struct in_addr ipv4_local_subnet;
diff --git a/main.c b/main.c
index 9e796fd..e973bf3 100644
--- a/main.c
+++ b/main.c
@@ -142,7 +142,7 @@
// following line causes XLAT failure in permissive mode.
unsetenv("ANDROID_DNS_MODE");
- configure_interface(uplink_interface, plat_prefix, v4_addr, v6_addr, &tunnel, net_id);
+ configure_interface(uplink_interface, plat_prefix, v4_addr, v6_addr, &tunnel, net_id, mark);
// Drop all remaining capabilities.
set_capability(0);
diff --git a/mtu.c b/mtu.c
deleted file mode 100644
index 472bd4e..0000000
--- a/mtu.c
+++ /dev/null
@@ -1,49 +0,0 @@
-/*
- * 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.
- *
- * mtu.c - get interface mtu
- */
-
-#include <net/if.h>
-#include <stdlib.h>
-#include <string.h>
-#include <sys/ioctl.h>
-#include <sys/socket.h>
-#include <sys/types.h>
-#include <unistd.h>
-
-#include "mtu.h"
-
-/* function: getifmtu
- * returns the interface mtu or -1 on failure
- * ifname - interface name
- */
-int getifmtu(const char *ifname) {
- int fd;
- struct ifreq if_mtu;
-
- fd = socket(AF_INET, SOCK_STREAM | SOCK_CLOEXEC, 0);
- if (fd < 0) {
- return -1;
- }
- strncpy(if_mtu.ifr_name, ifname, IFNAMSIZ);
- if_mtu.ifr_name[IFNAMSIZ - 1] = '\0';
- if (ioctl(fd, SIOCGIFMTU, &if_mtu) < 0) {
- close(fd);
- return -1;
- }
- close(fd);
- return if_mtu.ifr_mtu;
-}
diff --git a/mtu.h b/mtu.h
deleted file mode 100644
index c330c24..0000000
--- a/mtu.h
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * 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.
- *
- * mtu.c - get interface mtu
- */
-
-#ifndef __MTU_H__
-#define __MTU_H__
-
-int getifmtu(const char *ifname);
-
-#endif
