netdev - [RFC v2 PATCH 2/5] seg6: Obsolete unused SRH flags

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Message-Id: <1559933708-13947-3-git-send-email-tom@quantonium.net>
Date:   Fri,  7 Jun 2019 11:55:05 -0700
From:   Tom Herbert <tom@...bertland.com>
To:     davem@...emloft.net, netdev@...r.kernel.org, dlebrun@...gle.com
Cc:     Tom Herbert <tom@...ntonium.net>
Subject: [RFC v2 PATCH 2/5] seg6: Obsolete unused SRH flags

Currently no flags are defined for segment routing in
draft-ietf-6man-segment-routing-header-19. Mark them as being
obsolete.

The HMAC flag is the only one used by the stack. This needs
additional consideration. Rewrite sr_has_hmac in uapi/linux/seg6.h
to properly parse a segment routing header as opposed to relying
on the now obsolete flag.

Signed-off-by: Tom Herbert <tom@...ntonium.net>
---
 include/uapi/linux/seg6.h | 43 ++++++++++++++++++++++++++++++++++++-------
 1 file changed, 36 insertions(+), 7 deletions(-)

diff --git a/include/uapi/linux/seg6.h b/include/uapi/linux/seg6.h
index 3a7d324..0d19a9c 100644
--- a/include/uapi/linux/seg6.h
+++ b/include/uapi/linux/seg6.h
@@ -33,11 +33,10 @@ struct ipv6_sr_hdr {
 	struct in6_addr segments[0];
 };
 
-#define SR6_FLAG1_PROTECTED	(1 << 6)
-#define SR6_FLAG1_OAM		(1 << 5)
-#define SR6_FLAG1_ALERT		(1 << 4)
-#define SR6_FLAG1_HMAC		(1 << 3)
-
+#define SR6_FLAG1_PROTECTED	(1 << 6)	/* obsoleted */
+#define SR6_FLAG1_OAM		(1 << 5)	/* obsoleted */
+#define SR6_FLAG1_ALERT		(1 << 4)	/* obsoleted */
+#define SR6_FLAG1_HMAC		(1 << 3)	/* obsoleted */
 
 #define SR6_TLV_INGRESS		1	/* obsoleted */
 #define SR6_TLV_EGRESS		2	/* obsoleted */
@@ -47,12 +46,42 @@ struct ipv6_sr_hdr {
 #define SR6_TLV_PADN		1
 #define SR6_TLV_HMAC		5
 
-#define sr_has_hmac(srh) ((srh)->flags & SR6_FLAG1_HMAC)
-
 struct sr6_tlv {
 	__u8 type;
 	__u8 len;
 	__u8 data[0];
 };
 
+static inline int sr_hmac_offset(struct ipv6_sr_hdr *srh)
+{
+	unsigned char *opt = (unsigned char *)srh;
+	unsigned int off = sizeof(*srh) + ((srh->first_segment + 1) << 4);
+	int len = ((srh->hdrlen + 1) << 8) - off;
+	unsigned int optlen;
+
+	while (len > 0) {
+		switch (opt[off]) {
+		case SR6_TLV_PAD1:
+			optlen = 1;
+			break;
+		case SR6_TLV_HMAC:
+			return off;
+		default:
+			if (len < sizeof(struct sr6_tlv))
+				return 0;
+
+			optlen = sizeof(struct sr6_tlv) +
+				 ((struct sr6_tlv *)&opt[off])->len;
+			break;
+		}
+
+		off += optlen;
+		len -= optlen;
+	}
+
+	return 0;
+}
+
+#define sr_has_hmac(srh) (!!sr_hmac_offset(srh))
+
 #endif
-- 
2.7.4