[PATCH net-next V5 0/6] add support for RFC 8335 PROBE

The popular utility ping has several severe limitations, such as the
inability to query specific interfaces on a node and requiring
bidirectional connectivity between the probing and probed interfaces.
RFC 8335 attempts to solve these limitations by creating the new utility
PROBE which is a specialized ICMP message that makes use of the ICMP
Extension Structure outlined in RFC 4884.

This patchset adds definitions for the ICMP Extended Echo Request and
Reply (PROBE) types for both IPV4 and IPV6, adds a sysctl to enable
responses to PROBE messages, expands the list of supported ICMP messages
to accommodate PROBE types, and adds functionality to respond to PROBE
requests.

Changes:
v1 -> v2:
 - Add AFI definitions
 - Switch to functions such as dev_get_by_name and ip_dev_find to lookup
   net devices

v2 -> v3:
Suggested by Willem de Bruijn [off-list ref]
 - Add verification of incoming messages before looking up netdev
 - Add prefix for PROBE specific defined variables
 - Use proc_dointvec_minmax with zero and one for sysctl
 - Create struct icmp_ext_echo_iio for parsing incoming packets
Reported-by: kernel test robot <redacted>
Reported-by: Dan Carpenter <redacted>
 - Include net/addrconf.h library for ipv6_dev_find

v3 -> v4:
 - Use in_addr instead of __be32 for storing IPV4 addresses
 - Use IFNAMSIZ to statically allocate space for name in
   icmp_ext_echo_iio
Suggested by Willem de Bruijn [off-list ref]
 - Use skb_header_pointer to verify fields in incoming message
 - Add check to ensure that extobj_hdr.length is valid
 - Check to ensure object payload is padded with ASCII NULL characters
   when probing by name, as specified by RFC 8335
 - Statically allocate buff using IFNAMSIZ
 - Add rcu blocking around ipv6_dev_find
 - Use __in_dev_get_rcu to access IPV4 addresses of identified
   net_device
 - Remove check for ICMPV6 PROBE types

v4 -> v5:
 - Statically allocate buff to size IFNAMSIZ on declaration
 - Remove goto probe in favor of single branch
 - Remove strict check for incoming PROBE request padding to nearest
   32-bit boundary
Reported-by: kernel test robot <redacted>
 - Use rcu_dereference when accessing i6_ptr in net_device
 - Add ipv6_find_dev into ipv6_stub for use in icmp.c

Andreas Roeseler (6):
  icmp: add support for RFC 8335 PROBE
  ICMPV6: add support for RFC 8335 PROBE
  net: add sysctl for enabling RFC 8335 PROBE messages
  net: add support for sending RFC 8335 PROBE messages
  ipv6: add ipv6_dev_find to stubs
  icmp: add response to RFC 8335 PROBE messages

 include/net/ipv6_stubs.h    |   2 +
 include/net/netns/ipv4.h    |   1 +
 include/uapi/linux/icmp.h   |  42 ++++++++++++
 include/uapi/linux/icmpv6.h |   3 +
 net/ipv4/icmp.c             | 127 ++++++++++++++++++++++++++++++++----
 net/ipv4/ping.c             |   4 +-
 net/ipv4/sysctl_net_ipv4.c  |   9 +++
 net/ipv6/addrconf_core.c    |   7 ++
 net/ipv6/af_inet6.c         |   1 +
 9 files changed, 182 insertions(+), 14 deletions(-)

-- 
2.17.1

Add definitions for PROBE ICMP types and codes.

Add AFI definitions for IP and IPV6 as specified by IANA

Add a struct to represent the additional header when probing by IP
address (ctype == 3) for use in parsing incoming PROBE messages

Add a struct to represent the entire Interface Identification Object
(IIO) section of an incoming PROBE packet

Signed-off-by: Andreas Roeseler <redacted>
---
Changes:
v1 -> v2:
 - Add AFI_IP and AFI_IP6 definitions

v2 -> v3:
Suggested by Willem de Bruijn [off-list ref]
 - Add prefix for PROBE specific defined variables
 - Create struct icmp_ext_echo_iio for parsing incoming packet

v3 -> v4:
 - Use in_addr instead of __be32 for storing IPV4 addresses
 - Use IFNAMSIZ to statically allocate space for name in
   icmp_ext_echo_iio 

v4 -> v5:
 - Use __be32 instead of __u32 in defined structs
---
 include/uapi/linux/icmp.h | 42 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/include/uapi/linux/icmp.h b/include/uapi/linux/icmp.h
index fb169a50895e..222325d1d80e 100644
--- a/include/uapi/linux/icmp.h
+++ b/include/uapi/linux/icmp.h

@@ -20,6 +20,9 @@
 
 #include <linux/types.h>
 #include <asm/byteorder.h>
+#include <linux/in.h>
+#include <linux/if.h>
+#include <linux/in6.h>
 
 #define ICMP_ECHOREPLY		0	/* Echo Reply			*/
 #define ICMP_DEST_UNREACH	3	/* Destination Unreachable	*/

@@ -66,6 +69,23 @@
 #define ICMP_EXC_TTL		0	/* TTL count exceeded		*/
 #define ICMP_EXC_FRAGTIME	1	/* Fragment Reass time exceeded	*/
 
+/* Codes for EXT_ECHO (PROBE) */
+#define ICMP_EXT_ECHO		42
+#define ICMP_EXT_ECHOREPLY	43
+#define ICMP_EXT_MAL_QUERY	1	/* Malformed Query */
+#define ICMP_EXT_NO_IF		2	/* No such Interface */
+#define ICMP_EXT_NO_TABLE_ENT	3	/* No such Table Entry */
+#define ICMP_EXT_MULT_IFS	4	/* Multiple Interfaces Satisfy Query */
+
+/* Constants for EXT_ECHO (PROBE) */
+#define EXT_ECHOREPLY_ACTIVE	(1 << 2)/* active bit in reply message */
+#define EXT_ECHOREPLY_IPV4	(1 << 1)/* ipv4 bit in reply message */
+#define EXT_ECHOREPLY_IPV6	1	/* ipv6 bit in reply message */
+#define EXT_ECHO_CTYPE_NAME	1
+#define EXT_ECHO_CTYPE_INDEX	2
+#define EXT_ECHO_CTYPE_ADDR	3
+#define ICMP_AFI_IP		1	/* Address Family Identifier for ipv4 */
+#define ICMP_AFI_IP6		2	/* Address Family Identifier for ipv6 */
 
 struct icmphdr {
   __u8		type;

@@ -118,4 +138,26 @@ struct icmp_extobj_hdr {
 	__u8		class_type;
 };
 
+/* RFC 8335: 2.1 Header for c-type 3 payload */
+struct icmp_ext_echo_ctype3_hdr {
+	__be16		afi;
+	__u8		addrlen;
+	__u8		reserved;
+};
+
+/* RFC 8335: 2.1 Interface Identification Object */
+struct icmp_ext_echo_iio {
+	struct icmp_extobj_hdr extobj_hdr;
+	union {
+		char name[IFNAMSIZ];
+		__be32 ifindex;
+		struct {
+			struct icmp_ext_echo_ctype3_hdr ctype3_hdr;
+			union {
+				struct in_addr	ipv4_addr;
+				struct in6_addr	ipv6_addr;
+			} ip_addr;
+		} addr;
+	} ident;
+};
 #endif /* _UAPI_LINUX_ICMP_H */

-- 
2.17.1

Modify the ping_supported function to support PROBE message types. This
allows tools such as the ping command in the iputils package to be
modified to send PROBE requests through the existing framework for
sending ping requests.

Signed-off-by: Andreas Roeseler <redacted>
---
 net/ipv4/ping.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index 8b943f85fff9..1c9f71a37258 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c

@@ -453,7 +453,9 @@ EXPORT_SYMBOL_GPL(ping_bind);
 static inline int ping_supported(int family, int type, int code)
 {
 	return (family == AF_INET && type == ICMP_ECHO && code == 0) ||
-	       (family == AF_INET6 && type == ICMPV6_ECHO_REQUEST && code == 0);
+	       (family == AF_INET && type == ICMP_EXT_ECHO && code == 0) ||
+	       (family == AF_INET6 && type == ICMPV6_ECHO_REQUEST && code == 0) ||
+	       (family == AF_INET6 && type == ICMPV6_EXT_ECHO_REQUEST && code == 0);
 }
 
 /*

-- 
2.17.1

Add definitions for the ICMPV6 type of Extended Echo Request and
Extended Echo Reply, as defined by sections 2 and 3 of RFC 8335.

Signed-off-by: Andreas Roeseler <redacted>
---
 include/uapi/linux/icmpv6.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/uapi/linux/icmpv6.h b/include/uapi/linux/icmpv6.h
index 0564fd7ccde4..ecaece3af38d 100644
--- a/include/uapi/linux/icmpv6.h
+++ b/include/uapi/linux/icmpv6.h

@@ -140,6 +140,9 @@ struct icmp6hdr {
 #define ICMPV6_UNK_OPTION		2
 #define ICMPV6_HDR_INCOMP		3
 
+/* Codes for EXT_ECHO (PROBE) */
+#define ICMPV6_EXT_ECHO_REQUEST		160
+#define ICMPV6_EXT_ECHO_REPLY		161
 /*
  *	constants for (set|get)sockopt
  */

-- 
2.17.1

Section 8 of RFC 8335 specifies potential security concerns of
responding to PROBE requests, and states that nodes that support PROBE
functionality MUST be able to enable/disable responses and that
responses MUST be disabled by default

Signed-off-by: Andreas Roeseler <redacted>
---
Changes:
v1 -> v2:
 - Combine patches related to sysctl

v2 -> v3:
Suggested by Willem de Bruijn [off-list ref]
 - Use proc_dointvec_minmax with zero and one
---
 include/net/netns/ipv4.h   | 1 +
 net/ipv4/sysctl_net_ipv4.c | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 70a2a085dd1a..362388ab40c8 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h

@@ -85,6 +85,7 @@ struct netns_ipv4 {
 #endif
 
 	int sysctl_icmp_echo_ignore_all;
+	int sysctl_icmp_echo_enable_probe;
 	int sysctl_icmp_echo_ignore_broadcasts;
 	int sysctl_icmp_ignore_bogus_error_responses;
 	int sysctl_icmp_ratelimit;

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index f55095d3ed16..fec3f142d8c9 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c

@@ -599,6 +599,15 @@ static struct ctl_table ipv4_net_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec
 	},
+	{
+		.procname	= "icmp_echo_enable_probe",
+		.data		= &init_net.ipv4.sysctl_icmp_echo_enable_probe,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE
+	},
 	{
 		.procname	= "icmp_echo_ignore_broadcasts",
 		.data		= &init_net.ipv4.sysctl_icmp_echo_ignore_broadcasts,

-- 
2.17.1

Add ipv6_dev_find to ipv6_stub to allow lookup of net_devices by IPV6
address in net/ipv4/icmp.c.

Signed-off-by: Andreas Roeseler <redacted>
---
 include/net/ipv6_stubs.h | 2 ++
 net/ipv6/addrconf_core.c | 7 +++++++
 net/ipv6/af_inet6.c      | 1 +
 3 files changed, 10 insertions(+)

diff --git a/include/net/ipv6_stubs.h b/include/net/ipv6_stubs.h
index 8fce558b5fea..afbce90c4480 100644
--- a/include/net/ipv6_stubs.h
+++ b/include/net/ipv6_stubs.h

@@ -66,6 +66,8 @@ struct ipv6_stub {
 
 	int (*ipv6_fragment)(struct net *net, struct sock *sk, struct sk_buff *skb,
 			     int (*output)(struct net *, struct sock *, struct sk_buff *));
+	struct net_device *(*ipv6_dev_find)(struct net *net, const struct in6_addr *addr,
+					    struct net_device *dev);
 };
 extern const struct ipv6_stub *ipv6_stub __read_mostly;
 

diff --git a/net/ipv6/addrconf_core.c b/net/ipv6/addrconf_core.c
index c70c192bc91b..8f0b6024eba8 100644
--- a/net/ipv6/addrconf_core.c
+++ b/net/ipv6/addrconf_core.c

@@ -198,6 +198,12 @@ static int eafnosupport_ipv6_fragment(struct net *net, struct sock *sk, struct s
 	return -EAFNOSUPPORT;
 }
 
+static struct net_device *eafnosupport_ipv6_dev_find(struct net *net, const struct in6_addr *addr,
+						     struct net_device *dev)
+{
+	return ERR_PTR(-EAFNOSUPPORT);
+}
+
 const struct ipv6_stub *ipv6_stub __read_mostly = &(struct ipv6_stub) {
 	.ipv6_dst_lookup_flow = eafnosupport_ipv6_dst_lookup_flow,
 	.ipv6_route_input  = eafnosupport_ipv6_route_input,

@@ -209,6 +215,7 @@ const struct ipv6_stub *ipv6_stub __read_mostly = &(struct ipv6_stub) {
 	.fib6_nh_init	   = eafnosupport_fib6_nh_init,
 	.ip6_del_rt	   = eafnosupport_ip6_del_rt,
 	.ipv6_fragment	   = eafnosupport_ipv6_fragment,
+	.ipv6_dev_find     = eafnosupport_ipv6_dev_find,
 };
 EXPORT_SYMBOL_GPL(ipv6_stub);
 

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 802f5111805a..f0b860aecc2f 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c

@@ -1032,6 +1032,7 @@ static const struct ipv6_stub ipv6_stub_impl = {
 #endif
 	.nd_tbl	= &nd_tbl,
 	.ipv6_fragment = ip6_fragment,
+	.ipv6_dev_find = ipv6_dev_find,
 };
 
 static const struct ipv6_bpf_stub ipv6_bpf_stub_impl = {

-- 
2.17.1

Modify the icmp_rcv function to check PROBE messages and call icmp_echo
if a PROBE request is detected.

Modify the existing icmp_echo function to respond ot both ping and PROBE
requests.

This was tested using a custom modification to the iputils package and
wireshark. It supports IPV4 probing by name, ifindex, and probing by
both IPV4 and IPV6 addresses. It currently does not support responding
to probes off the proxy node (see RFC 8335 Section 2).

The modification to the iputils package is still in development and can
be found here: https://github.com/Juniper-Clinic-2020/iputils.git. It
supports full sending functionality of PROBE requests, but currently
does not parse the response messages, which is why Wireshark is required
to verify the sent and recieved PROBE messages. The modification adds
the ``-e'' flag to the command which allows the user to specify the
interface identifier to query the probed host. An example usage would be
<./ping -4 -e 1 [destination]> to send a PROBE request of ifindex 1 to the
destination node.

Signed-off-by: Andreas Roeseler <redacted>
---
Changes:
v1 -> v2:
 - Reorder variable declarations to follow coding style
 - Switch to functions such as dev_get_by_name and ip_dev_find to lookup
   net devices

v2 -> v3:
Suggested by Willem de Bruijn [off-list ref]
 - Add verification of incoming messages before looking up netdev
Reported-by: kernel test robot <redacted>
Reported-by: Dan Carpenter <redacted>
 - Include net/addrconf.h library for ipv6_dev_find

v3 -> v4:
Suggested by Willem de Bruijn [off-list ref]
 - Use skb_header_pointer to verify fields in incoming message
 - Add check to ensure that extobj_hdr.length is valid
 - Check to ensure object payload is padded with ASCII NULL characters
   when probing by name, as specified by RFC 8335
 - Statically allocate buff using IFNAMSIZ
 - Add rcu blocking around ipv6_dev_find
 - Use __in_dev_get_rcu to access IPV4 addresses of identified
   net_device
 - Remove check for ICMPV6 PROBE types

v4 -> v5:
 - Statically allocate buff to size IFNAMSIZ on declaration
 - Remove goto probe in favor of single branch
 - Remove strict check for incoming PROBE requests padding to nearest
   32-bit boundary
Reported-by: kernel test robot <redacted>
 - Use rcu_dereference when accessing i6_ptr in net_device
---
 net/ipv4/icmp.c | 127 +++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 114 insertions(+), 13 deletions(-)

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 616e2dc1c8fa..2acf7d3a66cb 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c

@@ -971,7 +971,7 @@ static bool icmp_redirect(struct sk_buff *skb)
 }
 
 /*
- *	Handle ICMP_ECHO ("ping") requests.
+ *	Handle ICMP_ECHO ("ping") and ICMP_EXT_ECHO ("PROBE") requests.
  *
  *	RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
  *		  requests.

@@ -979,27 +979,118 @@ static bool icmp_redirect(struct sk_buff *skb)
  *		  included in the reply.
  *	RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
  *		  echo requests, MUST have default=NOT.
+ *	RFC 8335: 8 MUST have a config option to enable/disable ICMP
+ *		  Extended Echo Functionality, MUST be disabled by default
  *	See also WRT handling of options once they are done and working.
  */
 
 static bool icmp_echo(struct sk_buff *skb)
 {
+	struct icmp_ext_hdr *ext_hdr, _ext_hdr;
+	struct icmp_ext_echo_iio *iio, _iio;
+	struct icmp_bxm icmp_param;
+	struct net_device *dev;
+	char buff[IFNAMSIZ];
 	struct net *net;
+	u16 ident_len;
+	u8 status;
 
 	net = dev_net(skb_dst(skb)->dev);
-	if (!net->ipv4.sysctl_icmp_echo_ignore_all) {
-		struct icmp_bxm icmp_param;
+	/* should there be an ICMP stat for ignored echos? */
+	if (net->ipv4.sysctl_icmp_echo_ignore_all)
+		return true;
+
+	icmp_param.data.icmph	   = *icmp_hdr(skb);
+	icmp_param.skb		   = skb;
+	icmp_param.offset	   = 0;
+	icmp_param.data_len	   = skb->len;
+	icmp_param.head_len	   = sizeof(struct icmphdr);
 
-		icmp_param.data.icmph	   = *icmp_hdr(skb);
+	if (icmp_param.data.icmph.type == ICMP_ECHO) {
 		icmp_param.data.icmph.type = ICMP_ECHOREPLY;
-		icmp_param.skb		   = skb;
-		icmp_param.offset	   = 0;
-		icmp_param.data_len	   = skb->len;
-		icmp_param.head_len	   = sizeof(struct icmphdr);
-		icmp_reply(&icmp_param, skb);
+		goto send_reply;
 	}
-	/* should there be an ICMP stat for ignored echos? */
-	return true;
+	if (!net->ipv4.sysctl_icmp_echo_enable_probe)
+		return true;
+	/* We currently only support probing interfaces on the proxy node
+	 * Check to ensure L-bit is set
+	 */
+	if (!(ntohs(icmp_param.data.icmph.un.echo.sequence) & 1))
+		return true;
+	/* Clear status bits in reply message */
+	icmp_param.data.icmph.un.echo.sequence &= htons(0xFF00);
+	icmp_param.data.icmph.type = ICMP_EXT_ECHOREPLY;
+	ext_hdr = skb_header_pointer(skb, 0, sizeof(_ext_hdr), &_ext_hdr);
+	iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(_iio), &_iio);
+	if (!ext_hdr || !iio)
+		goto send_mal_query;
+	if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr))
+		goto send_mal_query;
+	ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio->extobj_hdr);
+	status = 0;
+	dev = NULL;
+	switch (iio->extobj_hdr.class_type) {
+	case EXT_ECHO_CTYPE_NAME:
+		if (ident_len >= IFNAMSIZ)
+			goto send_mal_query;
+		memset(buff, 0, sizeof(buff));
+		memcpy(buff, &iio->ident.name, ident_len);
+		dev = dev_get_by_name(net, buff);
+		break;
+	case EXT_ECHO_CTYPE_INDEX:
+		if (ident_len != sizeof(iio->ident.ifindex))
+			goto send_mal_query;
+		dev = dev_get_by_index(net, ntohl(iio->ident.ifindex));
+		break;
+	case EXT_ECHO_CTYPE_ADDR:
+		if (ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
+				 iio->ident.addr.ctype3_hdr.addrlen)
+			goto send_mal_query;
+		switch (ntohs(iio->ident.addr.ctype3_hdr.afi)) {
+		case ICMP_AFI_IP:
+			if (ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
+					 sizeof(struct in_addr))
+				goto send_mal_query;
+			dev = ip_dev_find(net, iio->ident.addr.ip_addr.ipv4_addr.s_addr);
+			break;
+#if IS_ENABLED(CONFIG_IPV6)
+		case ICMP_AFI_IP6:
+			if (ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
+					 sizeof(struct in6_addr))
+				goto send_mal_query;
+			rcu_read_lock();
+			dev = ipv6_stub->ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev);
+			if (dev)
+				dev_hold(dev);
+			rcu_read_unlock();
+			break;
+#endif
+		default:
+			goto send_mal_query;
+		}
+		break;
+	default:
+		goto send_mal_query;
+	}
+	if (!dev) {
+		icmp_param.data.icmph.code = ICMP_EXT_NO_IF;
+		goto send_reply;
+	}
+	/* Fill bits in reply message */
+	if (dev->flags & IFF_UP)
+		status |= EXT_ECHOREPLY_ACTIVE;
+	if (__in_dev_get_rcu(dev) && __in_dev_get_rcu(dev)->ifa_list)
+		status |= EXT_ECHOREPLY_IPV4;
+	if (!list_empty(&rcu_dereference(dev->ip6_ptr)->addr_list))
+		status |= EXT_ECHOREPLY_IPV6;
+	dev_put(dev);
+	icmp_param.data.icmph.un.echo.sequence |= htons(status);
+send_reply:
+	icmp_reply(&icmp_param, skb);
+		return true;
+send_mal_query:
+	icmp_param.data.icmph.code = ICMP_EXT_MAL_QUERY;
+	goto send_reply;
 }
 
 /*

@@ -1088,6 +1179,16 @@ int icmp_rcv(struct sk_buff *skb)
 	icmph = icmp_hdr(skb);
 
 	ICMPMSGIN_INC_STATS(net, icmph->type);
+
+	/* Check for ICMP Extended Echo (PROBE) messages */
+	if (icmph->type == ICMP_EXT_ECHO) {
+		/* We can't use icmp_pointers[].handler() because it is an array of
+		 * size NR_ICMP_TYPES + 1 (19 elements) and PROBE has code 42.
+		 */
+		success = icmp_echo(skb);
+		goto success_check;
+	}
+
 	/*
 	 *	18 is the highest 'known' ICMP type. Anything else is a mystery
 	 *

@@ -1097,7 +1198,6 @@ int icmp_rcv(struct sk_buff *skb)
 	if (icmph->type > NR_ICMP_TYPES)
 		goto error;
 
-
 	/*
 	 *	Parse the ICMP message
 	 */

@@ -1123,7 +1223,7 @@ int icmp_rcv(struct sk_buff *skb)
 	}
 
 	success = icmp_pointers[icmph->type].handler(skb);
-
+success_check:
 	if (success)  {
 		consume_skb(skb);
 		return NET_RX_SUCCESS;

@@ -1340,6 +1440,7 @@ static int __net_init icmp_sk_init(struct net *net)
 
 	/* Control parameters for ECHO replies. */
 	net->ipv4.sysctl_icmp_echo_ignore_all = 0;
+	net->ipv4.sysctl_icmp_echo_enable_probe = 0;
 	net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
 
 	/* Control parameter - ignore bogus broadcast responses? */

-- 
2.17.1

On 3/24/21 7:18 PM, Andreas Roeseler wrote:

Modify the icmp_rcv function to check PROBE messages and call icmp_echo
if a PROBE request is detected.

...

Where is sysctl_icmp_echo_enable_probe defined ?

Please include a cover letter, also add proper documentation for any new sysctl
in Documentation/networking/ip-sysctl.rst

On Wed, 2021-03-24 at 20:47 +0100, Eric Dumazet wrote:

On 3/24/21 7:18 PM, Andreas Roeseler wrote:

quoted

Modify the icmp_rcv function to check PROBE messages and call
icmp_echo
if a PROBE request is detected.

...

quoted

@@ -1340,6 +1440,7 @@ static int __net_init icmp_sk_init(struct net

*net)
 
        /* Control parameters for ECHO replies. */
        net->ipv4.sysctl_icmp_echo_ignore_all = 0;
+       net->ipv4.sysctl_icmp_echo_enable_probe = 0;
        net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
 
        /* Control parameter - ignore bogus broadcast responses? */

Where is sysctl_icmp_echo_enable_probe defined ?

It is defined in patch 3 of this patchset.

Please include a cover letter, also add proper documentation for any
new sysctl
in Documentation/networking/ip-sysctl.rst

Will do.

On Wed, Mar 24, 2021 at 2:20 PM Andreas Roeseler
[off-list ref] wrote:

Modify the icmp_rcv function to check PROBE messages and call icmp_echo
if a PROBE request is detected.

Modify the existing icmp_echo function to respond ot both ping and PROBE
requests.

This was tested using a custom modification to the iputils package and
wireshark. It supports IPV4 probing by name, ifindex, and probing by
both IPV4 and IPV6 addresses. It currently does not support responding
to probes off the proxy node (see RFC 8335 Section 2).

The modification to the iputils package is still in development and can
be found here: https://github.com/Juniper-Clinic-2020/iputils.git. It
supports full sending functionality of PROBE requests, but currently
does not parse the response messages, which is why Wireshark is required
to verify the sent and recieved PROBE messages. The modification adds
the ``-e'' flag to the command which allows the user to specify the
interface identifier to query the probed host. An example usage would be
<./ping -4 -e 1 [destination]> to send a PROBE request of ifindex 1 to the
destination node.

Signed-off-by: Andreas Roeseler <redacted>

 static bool icmp_echo(struct sk_buff *skb)
 {
+       struct icmp_ext_hdr *ext_hdr, _ext_hdr;
+       struct icmp_ext_echo_iio *iio, _iio;
+       struct icmp_bxm icmp_param;
+       struct net_device *dev;
+       char buff[IFNAMSIZ];
        struct net *net;
+       u16 ident_len;
+       u8 status;

        net = dev_net(skb_dst(skb)->dev);
-       if (!net->ipv4.sysctl_icmp_echo_ignore_all) {
-               struct icmp_bxm icmp_param;
+       /* should there be an ICMP stat for ignored echos? */
+       if (net->ipv4.sysctl_icmp_echo_ignore_all)
+               return true;
+
+       icmp_param.data.icmph      = *icmp_hdr(skb);
+       icmp_param.skb             = skb;
+       icmp_param.offset          = 0;
+       icmp_param.data_len        = skb->len;
+       icmp_param.head_len        = sizeof(struct icmphdr);

-               icmp_param.data.icmph      = *icmp_hdr(skb);
+       if (icmp_param.data.icmph.type == ICMP_ECHO) {
                icmp_param.data.icmph.type = ICMP_ECHOREPLY;
-               icmp_param.skb             = skb;
-               icmp_param.offset          = 0;
-               icmp_param.data_len        = skb->len;
-               icmp_param.head_len        = sizeof(struct icmphdr);
-               icmp_reply(&icmp_param, skb);
+               goto send_reply;
        }
-       /* should there be an ICMP stat for ignored echos? */
-       return true;
+       if (!net->ipv4.sysctl_icmp_echo_enable_probe)
+               return true;
+       /* We currently only support probing interfaces on the proxy node
+        * Check to ensure L-bit is set
+        */
+       if (!(ntohs(icmp_param.data.icmph.un.echo.sequence) & 1))
+               return true;
+       /* Clear status bits in reply message */
+       icmp_param.data.icmph.un.echo.sequence &= htons(0xFF00);
+       icmp_param.data.icmph.type = ICMP_EXT_ECHOREPLY;
+       ext_hdr = skb_header_pointer(skb, 0, sizeof(_ext_hdr), &_ext_hdr);
+       iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(_iio), &_iio);

This requires that the packet holds a full sizeof(_iio) that is
capable of storing an ipv6 address regardless of the class_type. That
is not required by the spec, I assume.

If not requiring that, do have to do bounds checking for each
individual case, e.g., that an ifname fits in the packet if that may
be shorter than IFNAMSIZ.

+       if (!ext_hdr || !iio)
+               goto send_mal_query;
+       if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr))
+               goto send_mal_query;
+       ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio->extobj_hdr);

As asked in v3: this can have negative overflow?

+       status = 0;
+       dev = NULL;
+       switch (iio->extobj_hdr.class_type) {
+       case EXT_ECHO_CTYPE_NAME:
+               if (ident_len >= IFNAMSIZ)
+                       goto send_mal_query;
+               memset(buff, 0, sizeof(buff));
+               memcpy(buff, &iio->ident.name, ident_len);
+               dev = dev_get_by_name(net, buff);
+               break;
+       case EXT_ECHO_CTYPE_INDEX:
+               if (ident_len != sizeof(iio->ident.ifindex))
+                       goto send_mal_query;
+               dev = dev_get_by_index(net, ntohl(iio->ident.ifindex));
+               break;
+       case EXT_ECHO_CTYPE_ADDR:
+               if (ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
+                                iio->ident.addr.ctype3_hdr.addrlen)
+                       goto send_mal_query;
+               switch (ntohs(iio->ident.addr.ctype3_hdr.afi)) {
+               case ICMP_AFI_IP:
+                       if (ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
+                                        sizeof(struct in_addr))
+                               goto send_mal_query;
+                       dev = ip_dev_find(net, iio->ident.addr.ip_addr.ipv4_addr.s_addr);
+                       break;
+#if IS_ENABLED(CONFIG_IPV6)
+               case ICMP_AFI_IP6:
+                       if (ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
+                                        sizeof(struct in6_addr))
+                               goto send_mal_query;
+                       rcu_read_lock();
+                       dev = ipv6_stub->ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev);
+                       if (dev)
+                               dev_hold(dev);
+                       rcu_read_unlock();

This rcu read-size critical is not needed, because the entire receive
path is wrapped in such a section. See, for instance,
netif_receive_skb_core.

Either that, or the __in_dev_get_rcu and rcu_deference below would
require a similar critical section.

On Sun, 2021-03-28 at 13:00 -0400, Willem de Bruijn wrote:

On Wed, Mar 24, 2021 at 2:20 PM Andreas Roeseler
[off-list ref] wrote:

quoted

quoted

+       if (!ext_hdr || !iio)
+               goto send_mal_query;
+       if (ntohs(iio->extobj_hdr.length) <= sizeof(iio-

quoted

extobj_hdr))

+               goto send_mal_query;
+       ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio-

quoted

extobj_hdr);

As asked in v3: this can have negative overflow?

The line above checks that iio->extobj_hdr.length is greater than the
size of iio->extobj_hdr.

On Mon, Mar 29, 2021 at 2:34 PM Andreas Roeseler
[off-list ref] wrote:

On Sun, 2021-03-28 at 13:00 -0400, Willem de Bruijn wrote:

quoted

On Wed, Mar 24, 2021 at 2:20 PM Andreas Roeseler
[off-list ref] wrote:

quoted

quoted

+       if (!ext_hdr || !iio)
+               goto send_mal_query;
+       if (ntohs(iio->extobj_hdr.length) <= sizeof(iio-

quoted

extobj_hdr))

+               goto send_mal_query;
+       ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio-

quoted

extobj_hdr);

As asked in v3: this can have negative overflow?

The line above checks that iio->extobj_hdr.length is greater than the
size of iio->extobj_hdr.

Completely missed that, clearly. Thanks, that's great, then.