netdev - [PATCH net-next V2 2/3] net/act_pedit: Support using offset relative to the conventional network headers

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Date:   Thu,  5 Jan 2017 11:54:53 +0200
From:   Amir Vadai <amir@...ai.me>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Jiri Pirko <jiri@...lanox.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        Hadar Har-Zion <hadarh@...lanox.com>,
        Amir Vadai <amir@...ai.me>
Subject: [PATCH net-next V2 2/3] net/act_pedit: Support using offset relative to the conventional network headers

Extend pedit to enable the user setting offset relative to network
headers. This change would enable to work with more complex header
schemes (vs the simple IPv4 case) where setting a fixed offset relative
to the network header is not enough. It is also forward looking to
enable hardware offloading of pedit.

The header type is embedded in the 8 MSB of the u32 key->shift which
were never used till now. Therefore backward compatibility is being
kept.

Usage example:
$ tc filter add dev enp0s9 protocol ip parent ffff: \
  flower \
    ip_proto tcp \
    dst_port 80 \
  action pedit munge tcp dport set 8080 pipe \
  action mirred egress redirect dev veth0

Will forward tcp port whose original dest port is 80, while modifying
the destination port to 8080.

Signed-off-by: Amir Vadai <amir@...ai.me>
Reviewed-by: Or Gerlitz <ogerlitz@...lanox.com>
---
 include/uapi/linux/tc_act/tc_pedit.h | 17 ++++++++++
 net/sched/act_pedit.c                | 65 +++++++++++++++++++++++++++++-------
 2 files changed, 70 insertions(+), 12 deletions(-)

diff --git a/include/uapi/linux/tc_act/tc_pedit.h b/include/uapi/linux/tc_act/tc_pedit.h
index 6389959a5157..604e6729ad38 100644
--- a/include/uapi/linux/tc_act/tc_pedit.h
+++ b/include/uapi/linux/tc_act/tc_pedit.h
@@ -32,4 +32,21 @@ struct tc_pedit_sel {
 };
 #define tc_pedit tc_pedit_sel
 
+#define PEDIT_TYPE_SHIFT 24
+#define PEDIT_TYPE_MASK 0xff
+
+#define PEDIT_TYPE_GET(_val) \
+	(((_val) >> PEDIT_TYPE_SHIFT) & PEDIT_TYPE_MASK)
+#define PEDIT_SHIFT_GET(_val) ((_val) & 0xff)
+
+enum pedit_header_type {
+	PEDIT_HDR_TYPE_RAW = 0,
+
+	PEDIT_HDR_TYPE_ETH = 1,
+	PEDIT_HDR_TYPE_IP4 = 2,
+	PEDIT_HDR_TYPE_IP6 = 3,
+	PEDIT_HDR_TYPE_TCP = 4,
+	PEDIT_HDR_TYPE_UDP = 5,
+};
+
 #endif
diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index b27c4daec88f..4b9c7184c752 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -119,18 +119,45 @@ static bool offset_valid(struct sk_buff *skb, int offset)
 	return true;
 }
 
+static int pedit_skb_hdr_offset(struct sk_buff *skb,
+				enum pedit_header_type htype, int *hoffset)
+{
+	int ret = -1;
+
+	switch (htype) {
+	case PEDIT_HDR_TYPE_ETH:
+		if (skb_mac_header_was_set(skb)) {
+			*hoffset = skb_mac_offset(skb);
+			ret = 0;
+		}
+		break;
+	case PEDIT_HDR_TYPE_RAW:
+	case PEDIT_HDR_TYPE_IP4:
+	case PEDIT_HDR_TYPE_IP6:
+		*hoffset = skb_network_offset(skb);
+		ret = 0;
+		break;
+	case PEDIT_HDR_TYPE_TCP:
+	case PEDIT_HDR_TYPE_UDP:
+		if (skb_transport_header_was_set(skb)) {
+			*hoffset = skb_transport_offset(skb);
+			ret = 0;
+		}
+		break;
+	};
+
+	return ret;
+}
+
 static int tcf_pedit(struct sk_buff *skb, const struct tc_action *a,
 		     struct tcf_result *res)
 {
 	struct tcf_pedit *p = to_pedit(a);
 	int i;
-	unsigned int off;
 
 	if (skb_unclone(skb, GFP_ATOMIC))
 		return p->tcf_action;
 
-	off = skb_network_offset(skb);
-
 	spin_lock(&p->tcf_lock);
 
 	tcf_lastuse_update(&p->tcf_tm);
@@ -141,20 +168,32 @@ static int tcf_pedit(struct sk_buff *skb, const struct tc_action *a,
 		for (i = p->tcfp_nkeys; i > 0; i--, tkey++) {
 			u32 *ptr, _data;
 			int offset = tkey->off;
+			int hoffset;
+			int rc;
+			enum pedit_header_type htype =
+				PEDIT_TYPE_GET(tkey->shift);
+
+			rc = pedit_skb_hdr_offset(skb, htype, &hoffset);
+			if (rc) {
+				pr_info("tc filter pedit bad header type specified (0x%x)\n",
+					htype);
+				goto bad;
+			}
 
 			if (tkey->offmask) {
 				char *d, _d;
 
-				if (!offset_valid(skb, off + tkey->at)) {
+				if (!offset_valid(skb, hoffset + tkey->at)) {
 					pr_info("tc filter pedit 'at' offset %d out of bounds\n",
-						off + tkey->at);
+						hoffset + tkey->at);
 					goto bad;
 				}
-				d = skb_header_pointer(skb, off + tkey->at, 1,
-						       &_d);
+				d = skb_header_pointer(skb,
+						       hoffset + tkey->at,
+						       1, &_d);
 				if (!d)
 					goto bad;
-				offset += (*d & tkey->offmask) >> tkey->shift;
+				offset += (*d & tkey->offmask) >> PEDIT_SHIFT_GET(tkey->shift);
 			}
 
 			if (offset % 4) {
@@ -163,19 +202,21 @@ static int tcf_pedit(struct sk_buff *skb, const struct tc_action *a,
 				goto bad;
 			}
 
-			if (!offset_valid(skb, off + offset)) {
+			if (!offset_valid(skb, hoffset + offset)) {
 				pr_info("tc filter pedit offset %d out of bounds\n",
-					offset);
+					hoffset + offset);
 				goto bad;
 			}
 
-			ptr = skb_header_pointer(skb, off + offset, 4, &_data);
+			ptr = skb_header_pointer(skb,
+						 hoffset + offset,
+						 4, &_data);
 			if (!ptr)
 				goto bad;
 			/* just do it, baby */
 			*ptr = ((*ptr & tkey->mask) ^ tkey->val);
 			if (ptr == &_data)
-				skb_store_bits(skb, off + offset, ptr, 4);
+				skb_store_bits(skb, hoffset + offset, ptr, 4);
 		}
 
 		goto done;
-- 
2.11.0