[RFC PATCH 15/16] gtp: add ability to send GTP controls headers

[Jonas Bonn <jonas@norrbonn.se>]

From: Pravin B Shelar <pbshelar@fb.com>

Please explain how this patch actually works... creation of the control
header makes sense, but I don't understand how sending of a
control header is actually triggered.

Signed-off-by: Jonas Bonn <jonas@norrbonn.se>
---
 drivers/net/gtp.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 668ed8a4836e..bbce2671de2d 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -683,6 +683,38 @@ static void gtp_push_header(struct sk_buff *skb, struct pdp_ctx *pctx,
 	}
 }
 
+static inline int gtp1_push_control_header(struct sk_buff *skb,
+					   struct pdp_ctx *pctx,
+					   struct gtpu_metadata *opts,
+					   struct net_device *dev)
+{
+	struct gtp1_header *gtp1c;
+	int payload_len;
+
+	if (opts->ver != GTP_METADATA_V1)
+		return -ENOENT;
+
+	if (opts->type == 0xFE) {
+		/* for end marker ignore skb data. */
+		netdev_dbg(dev, "xmit pkt with null data");
+		pskb_trim(skb, 0);
+	}
+	if (skb_cow_head(skb, sizeof(*gtp1c)) < 0)
+		return -ENOMEM;
+
+	payload_len = skb->len;
+
+	gtp1c = skb_push(skb, sizeof(*gtp1c));
+
+	gtp1c->flags	= opts->flags;
+	gtp1c->type	= opts->type;
+	gtp1c->length	= htons(payload_len);
+	gtp1c->tid	= htonl(pctx->u.v1.o_tei);
+	netdev_dbg(dev, "xmit control pkt: ver %d flags %x type %x pkt len %d tid %x",
+		   opts->ver, opts->flags, opts->type, skb->len, pctx->u.v1.o_tei);
+	return 0;
+}
+
 static int gtp_xmit_ip4(struct sk_buff *skb, struct net_device *dev)
 {
 	struct gtp_dev *gtp = netdev_priv(dev);
@@ -807,7 +839,16 @@ static int gtp_xmit_ip4(struct sk_buff *skb, struct net_device *dev)
 
 	skb_set_inner_protocol(skb, skb->protocol);
 
-	gtp_push_header(skb, pctx, &port);
+	if (unlikely(opts)) {
+		port = htons(GTP1U_PORT);
+		r = gtp1_push_control_header(skb, pctx, opts, dev);
+		if (r) {
+			netdev_info(dev, "cntr pkt error %d", r);
+			goto err_rt;
+		}
+	} else {
+		gtp_push_header(skb, pctx, &port);
+	}
 
 	iph = ip_hdr(skb);
 	netdev_dbg(dev, "gtp -> IP src: %pI4 dst: %pI4\n",
-- 
2.27.0