ipv6: ICMPV6: add response to ICMPV6 RFC 8335 PROBE messages

This patch builds off of commit 2b246b2569cd2ac6ff700d0dce56b8bae29b1842
and adds functionality to respond to ICMPV6 PROBE requests.

Add icmp_build_probe function to construct PROBE requests for both
ICMPV4 and ICMPV6.

Modify icmpv6_rcv to detect ICMPV6 PROBE messages and call the
icmpv6_echo_reply handler.

Modify icmpv6_echo_reply to build a PROBE response message based on the
queried interface.

This patch has been tested using a branch of the iputils git repo which can
be found here: https://github.com/Juniper-Clinic-2020/iputils/tree/probe-request

Signed-off-by: Andreas Roeseler <andreas.a.roeseler@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 41 insertions, 22 deletions

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 0a57f1892e7e..c695d294a5df 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -993,14 +993,8 @@ static bool icmp_redirect(struct sk_buff *skb)
 
 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);
 	/* should there be an ICMP stat for ignored echos? */
@@ -1013,20 +1007,46 @@ static bool icmp_echo(struct sk_buff *skb)
 	icmp_param.data_len	   = skb->len;
 	icmp_param.head_len	   = sizeof(struct icmphdr);
 
-	if (icmp_param.data.icmph.type == ICMP_ECHO) {
+	if (icmp_param.data.icmph.type == ICMP_ECHO)
 		icmp_param.data.icmph.type = ICMP_ECHOREPLY;
-		goto send_reply;
-	}
-	if (!net->ipv4.sysctl_icmp_echo_enable_probe)
+	else if (!icmp_build_probe(skb, &icmp_param.data.icmph))
 		return true;
+
+	icmp_reply(&icmp_param, skb);
+	return true;
+}
+
+/*	Helper for icmp_echo and icmpv6_echo_reply.
+ *	Searches for net_device that matches PROBE interface identifier
+ *		and builds PROBE reply message in icmphdr.
+ *
+ *	Returns false if PROBE responses are disabled via sysctl
+ */
+
+bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
+{
+	struct icmp_ext_hdr *ext_hdr, _ext_hdr;
+	struct icmp_ext_echo_iio *iio, _iio;
+	struct net *net = dev_net(skb->dev);
+	struct net_device *dev;
+	char buff[IFNAMSIZ];
+	u16 ident_len;
+	u8 status;
+
+	if (!net->ipv4.sysctl_icmp_echo_enable_probe)
+		return false;
+
 	/* 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;
+	if (!(ntohs(icmphdr->un.echo.sequence) & 1))
+		return false;
 	/* Clear status bits in reply message */
-	icmp_param.data.icmph.un.echo.sequence &= htons(0xFF00);
-	icmp_param.data.icmph.type = ICMP_EXT_ECHOREPLY;
+	icmphdr->un.echo.sequence &= htons(0xFF00);
+	if (icmphdr->type == ICMP_EXT_ECHO)
+		icmphdr->type = ICMP_EXT_ECHOREPLY;
+	else
+		icmphdr->type = ICMPV6_EXT_ECHO_REPLY;
 	ext_hdr = skb_header_pointer(skb, 0, sizeof(_ext_hdr), &_ext_hdr);
 	/* Size of iio is class_type dependent.
 	 * Only check header here and assign length based on ctype in the switch statement
@@ -1087,8 +1107,8 @@ static bool icmp_echo(struct sk_buff *skb)
 		goto send_mal_query;
 	}
 	if (!dev) {
-		icmp_param.data.icmph.code = ICMP_EXT_CODE_NO_IF;
-		goto send_reply;
+		icmphdr->code = ICMP_EXT_CODE_NO_IF;
+		return true;
 	}
 	/* Fill bits in reply message */
 	if (dev->flags & IFF_UP)
@@ -1098,14 +1118,13 @@ static bool icmp_echo(struct sk_buff *skb)
 	if (!list_empty(&rcu_dereference(dev->ip6_ptr)->addr_list))
 		status |= ICMP_EXT_ECHOREPLY_IPV6;
 	dev_put(dev);
-	icmp_param.data.icmph.un.echo.sequence |= htons(status);
-send_reply:
-	icmp_reply(&icmp_param, skb);
-		return true;
+	icmphdr->un.echo.sequence |= htons(status);
+	return true;
 send_mal_query:
-	icmp_param.data.icmph.code = ICMP_EXT_CODE_MAL_QUERY;
-	goto send_reply;
+	icmphdr->code = ICMP_EXT_CODE_MAL_QUERY;
+	return true;
 }
+EXPORT_SYMBOL_GPL(icmp_build_probe);
 
 /*
  *	Handle ICMP Timestamp requests.