[PATCH net-next 2/3] icmp: prepare rfc 4884 for ipv6

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

From: Willem de Bruijn <willemb@google.com>

The RFC 4884 spec is largely the same between IPv4 and IPv6.
Factor out the IPv4 specific parts in preparation for IPv6 support:

- icmp types supported

- icmp header size, and thus offset to original datagram start

- datagram length field offset in icmp(6)hdr.

- datagram length field word size: 4B for IPv4, 8B for IPv6.

Signed-off-by: Willem de Bruijn <willemb@google.com>
---
 include/linux/icmp.h   |  3 ++-
 net/ipv4/icmp.c        | 17 ++++-------------
 net/ipv4/ip_sockglue.c | 14 +++++++++++++-
 3 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/include/linux/icmp.h b/include/linux/icmp.h
index 8fc38a34cb20..0af4d210ee31 100644
--- a/include/linux/icmp.h
+++ b/include/linux/icmp.h
@@ -37,6 +37,7 @@ static inline bool icmp_is_err(int type)
 }
 
 void ip_icmp_error_rfc4884(const struct sk_buff *skb,
-			   struct sock_ee_data_rfc4884 *out);
+			   struct sock_ee_data_rfc4884 *out,
+			   int thlen, int off);
 
 #endif	/* _LINUX_ICMP_H */
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 646d4fb72c07..1e70e98f14f8 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -1186,24 +1186,15 @@ static bool ip_icmp_error_rfc4884_validate(const struct sk_buff *skb, int off)
 }
 
 void ip_icmp_error_rfc4884(const struct sk_buff *skb,
-			   struct sock_ee_data_rfc4884 *out)
+			   struct sock_ee_data_rfc4884 *out,
+			   int thlen, int off)
 {
-	int hlen, off;
-
-	switch (icmp_hdr(skb)->type) {
-	case ICMP_DEST_UNREACH:
-	case ICMP_TIME_EXCEEDED:
-	case ICMP_PARAMETERPROB:
-		break;
-	default:
-		return;
-	}
+	int hlen;
 
 	/* original datagram headers: end of icmph to payload (skb->data) */
-	hlen = -skb_transport_offset(skb) - sizeof(struct icmphdr);
+	hlen = -skb_transport_offset(skb) - thlen;
 
 	/* per rfc 4884: minimal datagram length of 128 bytes */
-	off = icmp_hdr(skb)->un.reserved[1] * sizeof(u32);
 	if (off < 128 || off < hlen)
 		return;
 
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index a5ea02d7a183..6aa45fe0a676 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -389,6 +389,18 @@ int ip_ra_control(struct sock *sk, unsigned char on,
 	return 0;
 }
 
+static void ipv4_icmp_error_rfc4884(const struct sk_buff *skb,
+				    struct sock_ee_data_rfc4884 *out)
+{
+	switch (icmp_hdr(skb)->type) {
+	case ICMP_DEST_UNREACH:
+	case ICMP_TIME_EXCEEDED:
+	case ICMP_PARAMETERPROB:
+		ip_icmp_error_rfc4884(skb, out, sizeof(struct icmphdr),
+				      icmp_hdr(skb)->un.reserved[1] * 4);
+	}
+}
+
 void ip_icmp_error(struct sock *sk, struct sk_buff *skb, int err,
 		   __be16 port, u32 info, u8 *payload)
 {
@@ -412,7 +424,7 @@ void ip_icmp_error(struct sock *sk, struct sk_buff *skb, int err,
 
 	if (skb_pull(skb, payload - skb->data)) {
 		if (inet_sk(sk)->recverr_rfc4884)
-			ip_icmp_error_rfc4884(skb, &serr->ee.ee_rfc4884);
+			ipv4_icmp_error_rfc4884(skb, &serr->ee.ee_rfc4884);
 
 		skb_reset_transport_header(skb);
 		if (sock_queue_err_skb(sk, skb) == 0)
-- 
2.28.0.rc0.105.gf9edc3c819-goog