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

[Jonas Bonn]

From: Pravin B Shelar <pbshe...@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 <jo...@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