diff --git a/Cargo.toml b/Cargo.toml
index 11ebb98a14..0beb3d5308 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -135,7 +135,6 @@ math_libm = []
 no_trace = ["log/release_max_level_debug"]
 # for very verbose activity beyond trace level
 trace_tls = []
-ip6 = []
 
 [profile.dev]
 panic = "abort"
diff --git a/src/header/netdb/mod.rs b/src/header/netdb/mod.rs
index ea82382d45..e5fb4cb521 100644
--- a/src/header/netdb/mod.rs
+++ b/src/header/netdb/mod.rs
@@ -31,7 +31,6 @@ use crate::{
     raw_cell::RawCell,
 };
 
-#[cfg(feature = "ip6")]
 use crate::header::netinet_in::sockaddr_in6;
 
 #[cfg(target_os = "linux")]
@@ -1061,14 +1060,9 @@ pub unsafe extern "C" fn freeaddrinfo(res: *mut addrinfo) {
         if !bai.ai_addr.is_null() {
             if bai.ai_addrlen == mem::size_of::<sockaddr_in>() as socklen_t {
                 unsafe { drop(Box::from_raw(bai.ai_addr.cast::<sockaddr_in>())) };
+            } else if bai.ai_addrlen == mem::size_of::<sockaddr_in6>() as socklen_t {
+                unsafe { drop(Box::from_raw(bai.ai_addr.cast::<sockaddr_in6>())) };
             } else {
-                #[cfg(feature = "ip6")]
-                if bai.ai_addrlen == mem::size_of::<sockaddr_in6>() as socklen_t {
-                    unsafe { drop(Box::from_raw(bai.ai_addr.cast::<sockaddr_in6>())) };
-                } else {
-                    todo_skip!(0, "freeaddrinfo: unknown ai_addrlen {}", bai.ai_addrlen);
-                }
-                #[cfg(not(feature = "ip6"))]
                 todo_skip!(0, "freeaddrinfo: unknown ai_addrlen {}", bai.ai_addrlen);
             }
         }
diff --git a/src/header/netinet_in/mod.rs b/src/header/netinet_in/mod.rs
index a60c728af8..0e4ced5c15 100644
--- a/src/header/netinet_in/mod.rs
+++ b/src/header/netinet_in/mod.rs
@@ -22,7 +22,6 @@ pub struct in_addr {
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
-#[cfg(feature = "ip6")]
 #[repr(C)]
 pub struct in6_addr {
     pub s6_addr: [u8; 16],
@@ -40,7 +39,6 @@ pub struct sockaddr_in {
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
 #[repr(C)]
-#[cfg(feature = "ip6")]
 pub struct sockaddr_in6 {
     pub sin6_family: sa_family_t,
     pub sin6_port: in_port_t,
@@ -51,7 +49,6 @@ pub struct sockaddr_in6 {
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
 #[repr(C)]
-#[cfg(feature = "ip6")]
 pub struct ipv6_mreq {
     pub ipv6mr_multiaddr: in6_addr,
     pub ipv6mr_interface: u32,
@@ -61,7 +58,6 @@ pub struct ipv6_mreq {
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
 pub const INET_ADDRSTRLEN: c_int = 16;
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
-#[cfg(feature = "ip6")]
 pub const INET6_ADDRSTRLEN: c_int = 46;
 
 // IP options
@@ -86,7 +82,6 @@ pub const IPPROTO_UDP: u8 = 17;
 /// Non-POSIX.
 pub const IPPROTO_IDP: u8 = 22;
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
-#[cfg(feature = "ip6")]
 pub const IPPROTO_IPV6: u8 = 41;
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
 pub const IPPROTO_RAW: u8 = 0xff;
@@ -96,29 +91,20 @@ pub const IPPROTO_MAX: u8 = 0xff;
 /// Non-POSIX, see <https://www.man7.org/linux/man-pages/man7/ip.7.html>.
 pub const IP_TTL: c_int = 2;
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
-#[cfg(feature = "ip6")]
 pub const IPV6_UNICAST_HOPS: c_int = 16;
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
-#[cfg(feature = "ip6")]
 pub const IPV6_MULTICAST_IF: c_int = 17;
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
-#[cfg(feature = "ip6")]
 pub const IPV6_MULTICAST_HOPS: c_int = 18;
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
-#[cfg(feature = "ip6")]
 pub const IPV6_MULTICAST_LOOP: c_int = 19;
 /// Non-POSIX.
-#[cfg(feature = "ip6")]
 pub const IPV6_ADD_MEMBERSHIP: c_int = 20;
-#[cfg(feature = "ip6")]
 pub const IPV6_JOIN_GROUP: c_int = 20;
 /// Non-POSIX.
-#[cfg(feature = "ip6")]
 pub const IPV6_DROP_MEMBERSHIP: c_int = 21;
-#[cfg(feature = "ip6")]
 pub const IPV6_LEAVE_GROUP: c_int = 21;
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
-#[cfg(feature = "ip6")]
 pub const IPV6_V6ONLY: c_int = 26;
 /// Non-POSIX, see <https://www.man7.org/linux/man-pages/man7/ip.7.html>.
 pub const IP_MULTICAST_IF: c_int = 32;
@@ -180,14 +166,12 @@ pub struct group_source_req {
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
 #[unsafe(no_mangle)]
-#[cfg(feature = "ip6")]
 pub static in6addr_any: in6_addr = in6_addr {
     s6_addr: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
 };
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/netinet_in.h.html>.
 #[unsafe(no_mangle)]
-#[cfg(feature = "ip6")]
 pub static in6addr_loopback: in6_addr = in6_addr {
     s6_addr: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
 };
diff --git a/src/header/sys_socket/constants.rs b/src/header/sys_socket/constants.rs
index faeca8331a..f043163a74 100644
--- a/src/header/sys_socket/constants.rs
+++ b/src/header/sys_socket/constants.rs
@@ -168,7 +168,6 @@ pub const MCAST_LEAVE_SOURCE_GROUP: c_int = 47;
 /// Internet domain sockets for use with IPv4 sockets.
 pub const AF_INET: c_int = 2;
 /// Internet domain sockets for use with IPv6 sockets.
-#[cfg(feature = "ip6")]
 pub const AF_INET6: c_int = 10;
 /// Non-POSIX, see <https://www.man7.org/linux/man-pages/man7/unix.7.html>.
 ///