diff --git a/Makefile b/Makefile
index 8f96694..2735797 100644
--- a/Makefile
+++ b/Makefile
@@ -45,8 +45,8 @@ FLAGS += -DVERSION=\"$(VERSION)\"
 FLAGS += -DDUAL_STACK_SOCKETS=$(DUAL_STACK_SOCKETS)
 
 PASST_SRCS = arch.c arp.c checksum.c conf.c dhcp.c dhcpv6.c flow.c fwd.c \
-	icmp.c igmp.c inany.c iov.c isolation.c lineread.c log.c mld.c ndp.c \
-	netlink.c packet.c passt.c pasta.c pcap.c pif.c tap.c tcp.c \
+	icmp.c igmp.c inany.c iov.c ip.c isolation.c lineread.c log.c mld.c \
+	ndp.c netlink.c packet.c passt.c pasta.c pcap.c pif.c tap.c tcp.c \
 	tcp_splice.c udp.c util.c
 QRAP_SRCS = qrap.c
 SRCS = $(PASST_SRCS) $(QRAP_SRCS)
@@ -54,9 +54,9 @@ SRCS = $(PASST_SRCS) $(QRAP_SRCS)
 MANPAGES = passt.1 pasta.1 qrap.1
 
 PASST_HEADERS = arch.h arp.h checksum.h conf.h dhcp.h dhcpv6.h flow.h fwd.h \
-	flow_table.h icmp.h inany.h iov.h isolation.h lineread.h log.h ndp.h \
-	netlink.h packet.h passt.h pasta.h pcap.h pif.h siphash.h tap.h tcp.h \
-	tcp_conn.h tcp_splice.h udp.h util.h
+	flow_table.h icmp.h inany.h iov.h ip.h isolation.h lineread.h log.h \
+	ndp.h netlink.h packet.h passt.h pasta.h pcap.h pif.h siphash.h tap.h \
+	tcp.h tcp_conn.h tcp_splice.h udp.h util.h
 HEADERS = $(PASST_HEADERS) seccomp.h
 
 C := \#include <linux/tcp.h>\nstruct tcp_info x = { .tcpi_snd_wnd = 0 };
diff --git a/conf.c b/conf.c
index e630140..4a783b8 100644
--- a/conf.c
+++ b/conf.c
@@ -35,6 +35,7 @@
 #include <netinet/if_ether.h>
 
 #include "util.h"
+#include "ip.h"
 #include "passt.h"
 #include "netlink.h"
 #include "udp.h"
diff --git a/dhcp.c b/dhcp.c
index 1107728..ff4834a 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -25,6 +25,7 @@
 #include <limits.h>
 
 #include "util.h"
+#include "ip.h"
 #include "checksum.h"
 #include "packet.h"
 #include "passt.h"
diff --git a/flow.c b/flow.c
index d7974d5..5bb24cc 100644
--- a/flow.c
+++ b/flow.c
@@ -11,6 +11,7 @@
 #include <string.h>
 
 #include "util.h"
+#include "ip.h"
 #include "passt.h"
 #include "siphash.h"
 #include "inany.h"
diff --git a/fwd.c b/fwd.c
index 09650b2..a235d13 100644
--- a/fwd.c
+++ b/fwd.c
@@ -21,6 +21,7 @@
 #include <stdio.h>
 
 #include "util.h"
+#include "ip.h"
 #include "fwd.h"
 #include "passt.h"
 #include "lineread.h"
diff --git a/icmp.c b/icmp.c
index fb2fcaf..49d6dd9 100644
--- a/icmp.c
+++ b/icmp.c
@@ -33,6 +33,7 @@
 
 #include "packet.h"
 #include "util.h"
+#include "ip.h"
 #include "passt.h"
 #include "tap.h"
 #include "log.h"
diff --git a/inany.c b/inany.c
index 1c165b1..c8479a7 100644
--- a/inany.c
+++ b/inany.c
@@ -13,6 +13,7 @@
 #include <arpa/inet.h>
 
 #include "util.h"
+#include "ip.h"
 #include "siphash.h"
 #include "inany.h"
 
diff --git a/ip.c b/ip.c
new file mode 100644
index 0000000..2cc7f65
--- /dev/null
+++ b/ip.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/* PASST - Plug A Simple Socket Transport
+ *  for qemu/UNIX domain socket mode
+ *
+ * PASTA - Pack A Subtle Tap Abstraction
+ *  for network namespace/tap device mode
+ *
+ * ip.c - IP related functions
+ *
+ * Copyright (c) 2020-2021 Red Hat GmbH
+ * Author: Stefano Brivio <sbrivio@redhat.com>
+ */
+
+#include <stddef.h>
+#include "util.h"
+#include "ip.h"
+
+#define IPV6_NH_OPT(nh)							\
+	((nh) == 0   || (nh) == 43  || (nh) == 44  || (nh) == 50  ||	\
+	 (nh) == 51  || (nh) == 60  || (nh) == 135 || (nh) == 139 ||	\
+	 (nh) == 140 || (nh) == 253 || (nh) == 254)
+
+/**
+ * ipv6_l4hdr() - Find pointer to L4 header in IPv6 packet and extract protocol
+ * @p:		Packet pool, packet number @idx has IPv6 header at @offset
+ * @idx:	Index of packet in pool
+ * @offset:	Pre-calculated IPv6 header offset
+ * @proto:	Filled with L4 protocol number
+ * @dlen:	Data length (payload excluding header extensions), set on return
+ *
+ * Return: pointer to L4 header, NULL if not found
+ */
+char *ipv6_l4hdr(const struct pool *p, int idx, size_t offset, uint8_t *proto,
+		 size_t *dlen)
+{
+	const struct ipv6_opt_hdr *o;
+	const struct ipv6hdr *ip6h;
+	char *base;
+	int hdrlen;
+	uint8_t nh;
+
+	base = packet_get(p, idx, 0, 0, NULL);
+	ip6h = packet_get(p, idx, offset, sizeof(*ip6h), dlen);
+	if (!ip6h)
+		return NULL;
+
+	offset += sizeof(*ip6h);
+
+	nh = ip6h->nexthdr;
+	if (!IPV6_NH_OPT(nh))
+		goto found;
+
+	while ((o = packet_get_try(p, idx, offset, sizeof(*o), dlen))) {
+		nh = o->nexthdr;
+		hdrlen = (o->hdrlen + 1) * 8;
+
+		if (IPV6_NH_OPT(nh))
+			offset += hdrlen;
+		else
+			goto found;
+	}
+
+	return NULL;
+
+found:
+	if (nh == 59)
+		return NULL;
+
+	*proto = nh;
+	return base + offset;
+}
diff --git a/ip.h b/ip.h
new file mode 100644
index 0000000..9be4778
--- /dev/null
+++ b/ip.h
@@ -0,0 +1,86 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright (c) 2021 Red Hat GmbH
+ * Author: Stefano Brivio <sbrivio@redhat.com>
+ */
+
+#ifndef IP_H
+#define IP_H
+
+#include <netinet/ip.h>
+#include <netinet/ip6.h>
+
+#define IN4_IS_ADDR_UNSPECIFIED(a) \
+	(((struct in_addr *)(a))->s_addr == htonl_constant(INADDR_ANY))
+#define IN4_IS_ADDR_BROADCAST(a) \
+	(((struct in_addr *)(a))->s_addr == htonl_constant(INADDR_BROADCAST))
+#define IN4_IS_ADDR_LOOPBACK(a) \
+	(ntohl(((struct in_addr *)(a))->s_addr) >> IN_CLASSA_NSHIFT == IN_LOOPBACKNET)
+#define IN4_IS_ADDR_MULTICAST(a) \
+	(IN_MULTICAST(ntohl(((struct in_addr *)(a))->s_addr)))
+#define IN4_ARE_ADDR_EQUAL(a, b) \
+	(((struct in_addr *)(a))->s_addr == ((struct in_addr *)b)->s_addr)
+#define IN4ADDR_LOOPBACK_INIT \
+	{ .s_addr	= htonl_constant(INADDR_LOOPBACK) }
+#define IN4ADDR_ANY_INIT \
+	{ .s_addr	= htonl_constant(INADDR_ANY) }
+
+#define L2_BUF_IP4_INIT(proto)						\
+	{								\
+		.version	= 4,					\
+		.ihl		= 5,					\
+		.tos		= 0,					\
+		.tot_len	= 0,					\
+		.id		= 0,					\
+		.frag_off	= 0,					\
+		.ttl		= 0xff,					\
+		.protocol	= (proto),				\
+		.saddr		= 0,					\
+		.daddr		= 0,					\
+	}
+#define L2_BUF_IP4_PSUM(proto)	((uint32_t)htons_constant(0x4500) +	\
+				 (uint32_t)htons_constant(0xff00 | (proto)))
+
+#define L2_BUF_IP6_INIT(proto)						\
+	{								\
+		.priority	= 0,					\
+		.version	= 6,					\
+		.flow_lbl	= { 0 },				\
+		.payload_len	= 0,					\
+		.nexthdr	= (proto),				\
+		.hop_limit	= 255,					\
+		.saddr		= IN6ADDR_ANY_INIT,			\
+		.daddr		= IN6ADDR_ANY_INIT,			\
+	}
+
+struct ipv6hdr {
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wpedantic"
+#if __BYTE_ORDER == __BIG_ENDIAN
+	uint8_t			version:4,
+				priority:4;
+#else
+	uint8_t			priority:4,
+				version:4;
+#endif
+#pragma GCC diagnostic pop
+	uint8_t			flow_lbl[3];
+
+	uint16_t		payload_len;
+	uint8_t			nexthdr;
+	uint8_t			hop_limit;
+
+	struct in6_addr		saddr;
+	struct in6_addr		daddr;
+};
+
+struct ipv6_opt_hdr {
+	uint8_t			nexthdr;
+	uint8_t			hdrlen;
+	/*
+	 * TLV encoded option data follows.
+	 */
+} __attribute__((packed));	/* required for some archs */
+
+char *ipv6_l4hdr(const struct pool *p, int idx, size_t offset, uint8_t *proto,
+		 size_t *dlen);
+#endif /* IP_H */
diff --git a/ndp.c b/ndp.c
index 4c85ab8..c58f4b2 100644
--- a/ndp.c
+++ b/ndp.c
@@ -28,6 +28,7 @@
 
 #include "checksum.h"
 #include "util.h"
+#include "ip.h"
 #include "passt.h"
 #include "tap.h"
 #include "log.h"
diff --git a/qrap.c b/qrap.c
index 97f350a..d596706 100644
--- a/qrap.c
+++ b/qrap.c
@@ -32,6 +32,7 @@
 #include <linux/icmpv6.h>
 
 #include "util.h"
+#include "ip.h"
 #include "passt.h"
 #include "arp.h"
 
diff --git a/tap.c b/tap.c
index 3a66621..d35d894 100644
--- a/tap.c
+++ b/tap.c
@@ -45,6 +45,7 @@
 
 #include "checksum.h"
 #include "util.h"
+#include "ip.h"
 #include "iov.h"
 #include "passt.h"
 #include "arp.h"
diff --git a/tcp.c b/tcp.c
index 560d1d4..e0588f9 100644
--- a/tcp.c
+++ b/tcp.c
@@ -290,6 +290,7 @@
 
 #include "checksum.h"
 #include "util.h"
+#include "ip.h"
 #include "passt.h"
 #include "tap.h"
 #include "siphash.h"
diff --git a/tcp_splice.c b/tcp_splice.c
index 4957abb..d066112 100644
--- a/tcp_splice.c
+++ b/tcp_splice.c
@@ -49,6 +49,7 @@
 #include <sys/socket.h>
 
 #include "util.h"
+#include "ip.h"
 #include "passt.h"
 #include "log.h"
 #include "tcp_splice.h"
diff --git a/udp.c b/udp.c
index cb7c31f..26774df 100644
--- a/udp.c
+++ b/udp.c
@@ -113,6 +113,7 @@
 
 #include "checksum.h"
 #include "util.h"
+#include "ip.h"
 #include "siphash.h"
 #include "inany.h"
 #include "passt.h"
diff --git a/util.c b/util.c
index 81449b7..bac5a53 100644
--- a/util.c
+++ b/util.c
@@ -32,61 +32,6 @@
 #include "packet.h"
 #include "log.h"
 
-#define IPV6_NH_OPT(nh)							\
-	((nh) == 0   || (nh) == 43  || (nh) == 44  || (nh) == 50  ||	\
-	 (nh) == 51  || (nh) == 60  || (nh) == 135 || (nh) == 139 ||	\
-	 (nh) == 140 || (nh) == 253 || (nh) == 254)
-
-/**
- * ipv6_l4hdr() - Find pointer to L4 header in IPv6 packet and extract protocol
- * @p:		Packet pool, packet number @idx has IPv6 header at @offset
- * @idx:	Index of packet in pool
- * @offset:	Pre-calculated IPv6 header offset
- * @proto:	Filled with L4 protocol number
- * @dlen:	Data length (payload excluding header extensions), set on return
- *
- * Return: pointer to L4 header, NULL if not found
- */
-char *ipv6_l4hdr(const struct pool *p, int idx, size_t offset, uint8_t *proto,
-		 size_t *dlen)
-{
-	const struct ipv6_opt_hdr *o;
-	const struct ipv6hdr *ip6h;
-	char *base;
-	int hdrlen;
-	uint8_t nh;
-
-	base = packet_get(p, idx, 0, 0, NULL);
-	ip6h = packet_get(p, idx, offset, sizeof(*ip6h), dlen);
-	if (!ip6h)
-		return NULL;
-
-	offset += sizeof(*ip6h);
-
-	nh = ip6h->nexthdr;
-	if (!IPV6_NH_OPT(nh))
-		goto found;
-
-	while ((o = packet_get_try(p, idx, offset, sizeof(*o), dlen))) {
-		nh = o->nexthdr;
-		hdrlen = (o->hdrlen + 1) * 8;
-
-		if (IPV6_NH_OPT(nh))
-			offset += hdrlen;
-		else
-			goto found;
-	}
-
-	return NULL;
-
-found:
-	if (nh == 59)
-		return NULL;
-
-	*proto = nh;
-	return base + offset;
-}
-
 /**
  * sock_l4() - Create and bind socket for given L4, add to epoll list
  * @c:		Execution context
diff --git a/util.h b/util.h
index 5551349..25e54a7 100644
--- a/util.h
+++ b/util.h
@@ -110,22 +110,6 @@
 #define	htonl_constant(x)	(__bswap_constant_32(x))
 #endif
 
-#define IN4_IS_ADDR_UNSPECIFIED(a) \
-	(((struct in_addr *)(a))->s_addr == htonl_constant(INADDR_ANY))
-#define IN4_IS_ADDR_BROADCAST(a) \
-	(((struct in_addr *)(a))->s_addr == htonl_constant(INADDR_BROADCAST))
-#define IN4_IS_ADDR_LOOPBACK(a) \
-	(ntohl(((struct in_addr *)(a))->s_addr) >> IN_CLASSA_NSHIFT == IN_LOOPBACKNET)
-#define IN4_IS_ADDR_MULTICAST(a) \
-	(IN_MULTICAST(ntohl(((struct in_addr *)(a))->s_addr)))
-#define IN4_ARE_ADDR_EQUAL(a, b) \
-	(((struct in_addr *)(a))->s_addr == ((struct in_addr *)b)->s_addr)
-#define IN4ADDR_LOOPBACK_INIT \
-	{ .s_addr	= htonl_constant(INADDR_LOOPBACK) }
-#define IN4ADDR_ANY_INIT \
-	{ .s_addr	= htonl_constant(INADDR_ANY) }
-
-
 #define NS_FN_STACK_SIZE	(RLIMIT_STACK_VAL * 1024 / 8)
 int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags,
 	     void *arg);
@@ -138,34 +122,6 @@ int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags,
 			 (void *)(arg));				\
 	} while (0)
 
-#define L2_BUF_IP4_INIT(proto)						\
-	{								\
-		.version	= 4,					\
-		.ihl		= 5,					\
-		.tos		= 0,					\
-		.tot_len	= 0,					\
-		.id		= 0,					\
-		.frag_off	= 0,					\
-		.ttl		= 0xff,					\
-		.protocol	= (proto),				\
-		.saddr		= 0,					\
-		.daddr		= 0,					\
-	}
-#define L2_BUF_IP4_PSUM(proto)	((uint32_t)htons_constant(0x4500) +	\
-				 (uint32_t)htons_constant(0xff00 | (proto)))
-
-#define L2_BUF_IP6_INIT(proto)						\
-	{								\
-		.priority	= 0,					\
-		.version	= 6,					\
-		.flow_lbl	= { 0 },				\
-		.payload_len	= 0,					\
-		.nexthdr	= (proto),				\
-		.hop_limit	= 255,					\
-		.saddr		= IN6ADDR_ANY_INIT,			\
-		.daddr		= IN6ADDR_ANY_INIT,			\
-	}
-
 #define RCVBUF_BIG		(2UL * 1024 * 1024)
 #define SNDBUF_BIG		(4UL * 1024 * 1024)
 #define SNDBUF_SMALL		(128UL * 1024)
@@ -173,45 +129,13 @@ int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags,
 #include <net/if.h>
 #include <limits.h>
 #include <stdint.h>
-#include <netinet/ip6.h>
 
 #include "packet.h"
 
 struct ctx;
 
-struct ipv6hdr {
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wpedantic"
-#if __BYTE_ORDER == __BIG_ENDIAN
-	uint8_t			version:4,
-				priority:4;
-#else
-	uint8_t			priority:4,
-				version:4;
-#endif
-#pragma GCC diagnostic pop
-	uint8_t			flow_lbl[3];
-
-	uint16_t		payload_len;
-	uint8_t			nexthdr;
-	uint8_t			hop_limit;
-
-	struct in6_addr		saddr;
-	struct in6_addr		daddr;
-};
-
-struct ipv6_opt_hdr {
-	uint8_t			nexthdr;
-	uint8_t			hdrlen;
-	/*
-	 * TLV encoded option data follows.
-	 */
-} __attribute__((packed));	/* required for some archs */
-
 /* cppcheck-suppress funcArgNamesDifferent */
 __attribute__ ((weak)) int ffsl(long int i) { return __builtin_ffsl(i); }
-char *ipv6_l4hdr(const struct pool *p, int idx, size_t offset, uint8_t *proto,
-		 size_t *dlen);
 int sock_l4(const struct ctx *c, sa_family_t af, uint8_t proto,
 	    const void *bind_addr, const char *ifname, uint16_t port,
 	    uint32_t data);