diff --git a/service/native/libs/libclat/clatutils.cpp b/service/native/libs/libclat/clatutils.cpp
index 4a125ba..be86612 100644
--- a/service/native/libs/libclat/clatutils.cpp
+++ b/service/native/libs/libclat/clatutils.cpp
@@ -126,10 +126,19 @@
 
 // Picks a random interface ID that is checksum neutral with the IPv4 address and the NAT64 prefix.
 int generateIpv6Address(const char* iface, const in_addr v4, const in6_addr& nat64Prefix,
-                        in6_addr* v6) {
+                        in6_addr* v6, uint32_t mark) {
     int s = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, 0);
     if (s == -1) return -errno;
 
+    // Socket's mark affects routing decisions (network selection)
+    // An fwmark is necessary for clat to bypass the VPN during initialization.
+    if ((mark != MARK_UNSET) && setsockopt(s, SOL_SOCKET, SO_MARK, &mark, sizeof(mark))) {
+        int ret = errno;
+        ALOGE("setsockopt(SOL_SOCKET, SO_MARK) failed: %s", strerror(errno));
+        close(s);
+        return -ret;
+    }
+
     if (setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE, iface, strlen(iface) + 1) == -1) {
         close(s);
         return -errno;
diff --git a/service/native/libs/libclat/clatutils_test.cpp b/service/native/libs/libclat/clatutils_test.cpp
index 8cca1f4..abd4e81 100644
--- a/service/native/libs/libclat/clatutils_test.cpp
+++ b/service/native/libs/libclat/clatutils_test.cpp
@@ -202,7 +202,8 @@
     in6_addr v6;
     EXPECT_EQ(1, inet_pton(AF_INET6, "::", &v6));  // initialize as zero
 
-    EXPECT_EQ(-ENETUNREACH, generateIpv6Address(tun.name().c_str(), v4, nat64Prefix, &v6));
+    // 0u is MARK_UNSET
+    EXPECT_EQ(-ENETUNREACH, generateIpv6Address(tun.name().c_str(), v4, nat64Prefix, &v6, 0u));
     EXPECT_TRUE(IN6_IS_ADDR_ULA(&v6));
 
     tun.destroy();
diff --git a/service/native/libs/libclat/include/libclat/clatutils.h b/service/native/libs/libclat/include/libclat/clatutils.h
index 812c86e..991b193 100644
--- a/service/native/libs/libclat/include/libclat/clatutils.h
+++ b/service/native/libs/libclat/include/libclat/clatutils.h
@@ -24,7 +24,7 @@
 in_addr_t selectIpv4Address(const in_addr ip, int16_t prefixlen);
 void makeChecksumNeutral(in6_addr* v6, const in_addr v4, const in6_addr& nat64Prefix);
 int generateIpv6Address(const char* iface, const in_addr v4, const in6_addr& nat64Prefix,
-                        in6_addr* v6);
+                        in6_addr* v6, uint32_t mark);
 int detect_mtu(const struct in6_addr* plat_subnet, uint32_t plat_suffix, uint32_t mark);
 int configure_packet_socket(int sock, in6_addr* addr, int ifindex);