[RFC net-next 11/15] ipxlat: add ICMP informational translation paths

[Ralf Lici <ralf@mandelbit.com>]

Add ICMP informational message translation for both 4->6 and 6->4 paths
and wire the new ICMP translation units into the engine.

This introduces the protocol mapping and checksum update logic for echo
request/reply traffic, while ICMP error quoted-inner translation is
added in a follow-up commit.

Signed-off-by: Ralf Lici <ralf@mandelbit.com>
---
 drivers/net/ipxlat/Makefile       |  2 +
 drivers/net/ipxlat/icmp.h         | 43 ++++++++++++++
 drivers/net/ipxlat/icmp_46.c      | 95 +++++++++++++++++++++++++++++++
 drivers/net/ipxlat/icmp_64.c      | 92 ++++++++++++++++++++++++++++++
 drivers/net/ipxlat/translate_64.c |  1 +
 drivers/net/ipxlat/transport.c    | 11 ----
 drivers/net/ipxlat/transport.h    |  5 --
 7 files changed, 233 insertions(+), 16 deletions(-)
 create mode 100644 drivers/net/ipxlat/icmp.h
 create mode 100644 drivers/net/ipxlat/icmp_46.c
 create mode 100644 drivers/net/ipxlat/icmp_64.c

diff --git a/drivers/net/ipxlat/Makefile b/drivers/net/ipxlat/Makefile
index d7b7097aee5f..2ded504902e3 100644
--- a/drivers/net/ipxlat/Makefile
+++ b/drivers/net/ipxlat/Makefile
@@ -11,3 +11,5 @@ ipxlat-objs += transport.o
 ipxlat-objs += dispatch.o
 ipxlat-objs += translate_46.o
 ipxlat-objs += translate_64.o
+ipxlat-objs += icmp_46.o
+ipxlat-objs += icmp_64.o
diff --git a/drivers/net/ipxlat/icmp.h b/drivers/net/ipxlat/icmp.h
new file mode 100644
index 000000000000..52d681787d6a
--- /dev/null
+++ b/drivers/net/ipxlat/icmp.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*  IPXLAT - Stateless IP/ICMP Translation (SIIT) virtual device driver
+ *
+ *  Copyright (C) 2024- Alberto Leiva Popper <ydahhrk@gmail.com>
+ *  Copyright (C) 2026- Mandelbit SRL
+ *  Copyright (C) 2026- Daniel Gröber <dxld@darkboxed.org>
+ *
+ *  Author:	Alberto Leiva Popper <ydahhrk@gmail.com>
+ *		Antonio Quartulli <antonio@mandelbit.com>
+ *		Daniel Gröber <dxld@darkboxed.org>
+ *		Ralf Lici <ralf@mandelbit.com>
+ */
+
+#ifndef _NET_IPXLAT_ICMP_H_
+#define _NET_IPXLAT_ICMP_H_
+
+#include <linux/ipv6.h>
+
+#include "ipxlpriv.h"
+
+/**
+ * ipxlat_46_icmp - translate ICMP informational payload
+ *		    after outer 4->6 rewrite
+ * @ipxl: translator private context
+ * @skb: packet carrying ICMPv4 transport payload
+ *
+ * Return: 0 on success, negative errno on translation failure.
+ */
+int ipxlat_46_icmp(struct ipxlat_priv *ipxl, struct sk_buff *skb);
+
+/**
+ * ipxlat_64_icmp - translate ICMP informational payload
+ *		    after outer 6->4 rewrite
+ * @ipxlat: translator private context
+ * @skb: packet carrying ICMPv6 transport payload
+ * @in6: snapshot of original outer IPv6 header
+ *
+ * Return: 0 on success, negative errno on translation failure.
+ */
+int ipxlat_64_icmp(struct ipxlat_priv *ipxlat, struct sk_buff *skb,
+		   const struct ipv6hdr *in6);
+
+#endif /* _NET_IPXLAT_ICMP_H_ */
diff --git a/drivers/net/ipxlat/icmp_46.c b/drivers/net/ipxlat/icmp_46.c
new file mode 100644
index 000000000000..ad907f60416c
--- /dev/null
+++ b/drivers/net/ipxlat/icmp_46.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0
+/*  IPXLAT - Stateless IP/ICMP Translation (SIIT) virtual device driver
+ *
+ *  Copyright (C) 2024- Alberto Leiva Popper <ydahhrk@gmail.com>
+ *  Copyright (C) 2026- Mandelbit SRL
+ *  Copyright (C) 2026- Daniel Gröber <dxld@darkboxed.org>
+ *
+ *  Author:	Alberto Leiva Popper <ydahhrk@gmail.com>
+ *		Antonio Quartulli <antonio@mandelbit.com>
+ *		Daniel Gröber <dxld@darkboxed.org>
+ *		Ralf Lici <ralf@mandelbit.com>
+ */
+
+#include <linux/icmp.h>
+#include <linux/icmpv6.h>
+
+#include "icmp.h"
+#include "packet.h"
+#include "transport.h"
+
+static int ipxlat_46_map_icmp_info_type_code(const struct icmphdr *in,
+					     struct icmp6hdr *out)
+{
+	switch (in->type) {
+	case ICMP_ECHO:
+		out->icmp6_type = ICMPV6_ECHO_REQUEST;
+		out->icmp6_code = 0;
+		out->icmp6_identifier = in->un.echo.id;
+		out->icmp6_sequence = in->un.echo.sequence;
+		return 0;
+	case ICMP_ECHOREPLY:
+		out->icmp6_type = ICMPV6_ECHO_REPLY;
+		out->icmp6_code = 0;
+		out->icmp6_identifier = in->un.echo.id;
+		out->icmp6_sequence = in->un.echo.sequence;
+		return 0;
+	}
+
+	return -EPROTONOSUPPORT;
+}
+
+static void ipxlat_46_icmp_info_update_csum(const struct icmphdr *icmp4,
+					    struct icmp6hdr *icmp6,
+					    const struct ipv6hdr *ip6,
+					    const struct sk_buff *skb,
+					    unsigned int l4_off)
+{
+	struct icmp6hdr icmp6_zero;
+	struct icmphdr icmp4_zero;
+	__wsum csum;
+
+	icmp4_zero = *icmp4;
+	icmp4_zero.checksum = 0;
+	icmp6_zero = *icmp6;
+	icmp6_zero.icmp6_cksum = 0;
+	csum = ~csum_unfold(icmp4->checksum);
+	csum = csum_sub(csum, csum_partial(&icmp4_zero, sizeof(icmp4_zero), 0));
+	csum = csum_add(csum, csum_partial(&icmp6_zero, sizeof(icmp6_zero), 0));
+	icmp6->icmp6_cksum = csum_ipv6_magic(&ip6->saddr, &ip6->daddr,
+					     skb->len - l4_off,
+					     IPPROTO_ICMPV6, csum);
+}
+
+static int ipxlat_46_icmp_info_outer(struct sk_buff *skb)
+{
+	const unsigned int l4_off = skb_transport_offset(skb);
+	const struct icmphdr icmp4 = *icmp_hdr(skb);
+	const struct ipv6hdr *ip6 = ipv6_hdr(skb);
+	struct icmp6hdr *icmp6 = icmp6_hdr(skb);
+	int err;
+
+	err = ipxlat_46_map_icmp_info_type_code(&icmp4, icmp6);
+	if (unlikely(err))
+		return -EINVAL;
+
+	if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		icmp6->icmp6_cksum = ~csum_ipv6_magic(&ip6->saddr, &ip6->daddr,
+						      skb->len - l4_off,
+						      IPPROTO_ICMPV6, 0);
+		return ipxlat_set_partial_csum(skb, offsetof(struct icmp6hdr,
+							   icmp6_cksum));
+	}
+
+	ipxlat_46_icmp_info_update_csum(&icmp4, icmp6, ip6, skb, l4_off);
+	skb->ip_summed = CHECKSUM_NONE;
+	return 0;
+}
+
+int ipxlat_46_icmp(struct ipxlat_priv *ipxl, struct sk_buff *skb)
+{
+	if (unlikely(ipxlat_skb_cb(skb)->is_icmp_err))
+		return -EPROTONOSUPPORT;
+
+	return ipxlat_46_icmp_info_outer(skb);
+}
diff --git a/drivers/net/ipxlat/icmp_64.c b/drivers/net/ipxlat/icmp_64.c
new file mode 100644
index 000000000000..6b11aa638068
--- /dev/null
+++ b/drivers/net/ipxlat/icmp_64.c
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0
+/*  IPXLAT - Stateless IP/ICMP Translation (SIIT) virtual device driver
+ *
+ *  Copyright (C) 2024- Alberto Leiva Popper <ydahhrk@gmail.com>
+ *  Copyright (C) 2026- Mandelbit SRL
+ *  Copyright (C) 2026- Daniel Gröber <dxld@darkboxed.org>
+ *
+ *  Author:	Alberto Leiva Popper <ydahhrk@gmail.com>
+ *		Antonio Quartulli <antonio@mandelbit.com>
+ *		Daniel Gröber <dxld@darkboxed.org>
+ *		Ralf Lici <ralf@mandelbit.com>
+ */
+
+#include <linux/icmpv6.h>
+
+#include "icmp.h"
+#include "packet.h"
+#include "transport.h"
+
+static int ipxlat_64_map_icmp_info_type_code(const struct icmp6hdr *in,
+					     struct icmphdr *out)
+{
+	switch (in->icmp6_type) {
+	case ICMPV6_ECHO_REQUEST:
+		out->type = ICMP_ECHO;
+		out->code = 0;
+		out->un.echo.id = in->icmp6_identifier;
+		out->un.echo.sequence = in->icmp6_sequence;
+		return 0;
+	case ICMPV6_ECHO_REPLY:
+		out->type = ICMP_ECHOREPLY;
+		out->code = 0;
+		out->un.echo.id = in->icmp6_identifier;
+		out->un.echo.sequence = in->icmp6_sequence;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static __sum16 ipxlat_64_compute_icmp_info_csum(const struct ipv6hdr *in6,
+						const struct icmp6hdr *in_icmp6,
+						const struct icmphdr *out_icmp4,
+						unsigned int l4_len)
+{
+	struct icmp6hdr icmp6_zero;
+	struct icmphdr icmp4_zero;
+	__wsum csum, tmp;
+
+	icmp6_zero = *in_icmp6;
+	icmp6_zero.icmp6_cksum = 0;
+	icmp4_zero = *out_icmp4;
+	icmp4_zero.checksum = 0;
+
+	csum = ~csum_unfold(in_icmp6->icmp6_cksum);
+	tmp = ~csum_unfold(csum_ipv6_magic(&in6->saddr, &in6->daddr, l4_len,
+					   NEXTHDR_ICMP, 0));
+	csum = csum_sub(csum, tmp);
+	csum = csum_sub(csum, csum_partial(&icmp6_zero, sizeof(icmp6_zero), 0));
+	csum = csum_add(csum, csum_partial(&icmp4_zero, sizeof(icmp4_zero), 0));
+	return csum_fold(csum);
+}
+
+static int ipxlat_64_icmp_info(struct sk_buff *skb, const struct ipv6hdr *in6)
+{
+	struct icmp6hdr ic6_copy, *ic6;
+	struct icmphdr *ic4;
+	int err;
+
+	ic6 = icmp6_hdr(skb);
+	ic6_copy = *ic6;
+
+	ic4 = (struct icmphdr *)(skb->data + skb_transport_offset(skb));
+	err = ipxlat_64_map_icmp_info_type_code(&ic6_copy, ic4);
+	if (unlikely(err))
+		return err;
+
+	ic4->checksum =
+		ipxlat_64_compute_icmp_info_csum(in6, &ic6_copy, ic4,
+						 ipxlat_skb_datagram_len(skb));
+	skb->ip_summed = CHECKSUM_NONE;
+	return 0;
+}
+
+int ipxlat_64_icmp(struct ipxlat_priv *ipxl, struct sk_buff *skb,
+		   const struct ipv6hdr *in6)
+{
+	if (unlikely(ipxlat_skb_cb(skb)->is_icmp_err))
+		return -EPROTONOSUPPORT;
+
+	return ipxlat_64_icmp_info(skb, in6);
+}
diff --git a/drivers/net/ipxlat/translate_64.c b/drivers/net/ipxlat/translate_64.c
index 50a95fb75f9d..412d29214a43 100644
--- a/drivers/net/ipxlat/translate_64.c
+++ b/drivers/net/ipxlat/translate_64.c
@@ -16,6 +16,7 @@
 
 #include "translate_64.h"
 #include "address.h"
+#include "icmp.h"
 #include "packet.h"
 #include "transport.h"
 
diff --git a/drivers/net/ipxlat/transport.c b/drivers/net/ipxlat/transport.c
index 78548d0b8c22..3aa00c635916 100644
--- a/drivers/net/ipxlat/transport.c
+++ b/drivers/net/ipxlat/transport.c
@@ -338,14 +338,3 @@ int ipxlat_64_inner_udp(struct sk_buff *skb, const struct ipv6hdr *in6,
 		udp_new->check = CSUM_MANGLED_0;
 	return 0;
 }
-
-int ipxlat_46_icmp(struct ipxlat_priv *ipxlat, struct sk_buff *skb)
-{
-	return -EPROTONOSUPPORT;
-}
-
-int ipxlat_64_icmp(struct ipxlat_priv *ipxlat, struct sk_buff *skb,
-		   const struct ipv6hdr *outer6)
-{
-	return -EPROTONOSUPPORT;
-}
diff --git a/drivers/net/ipxlat/transport.h b/drivers/net/ipxlat/transport.h
index 0e69b98eafd0..9b6fe422b01f 100644
--- a/drivers/net/ipxlat/transport.h
+++ b/drivers/net/ipxlat/transport.h
@@ -100,9 +100,4 @@ int ipxlat_64_inner_tcp(struct sk_buff *skb, const struct ipv6hdr *in6,
 int ipxlat_64_inner_udp(struct sk_buff *skb, const struct ipv6hdr *in6,
 			const struct iphdr *out4, struct udphdr *udp_new);
 
-/* temporary ICMP stubs until ICMP translation support is introduced */
-int ipxlat_46_icmp(struct ipxlat_priv *ipxlat, struct sk_buff *skb);
-int ipxlat_64_icmp(struct ipxlat_priv *ipxlat, struct sk_buff *skb,
-		   const struct ipv6hdr *outer6);
-
 #endif /* _NET_IPXLAT_TRANSPORT_H_ */
-- 
2.53.0