[PATCH 0/3] pull request for net: batman-adv 2020-11-27

[PATCH 0/3] pull request for net: batman-adv 2020-11-27

[Simon Wunderlich]

Hi David, hi Jakub,

here are some more bugfixes for batman-adv which we would like to have integrated into net.

Please pull or let me know of any problem!

Thank you,
      Simon

The following changes since commit 14a2e551faea53d45bc11629a9dac88f88950ca7:

  batman-adv: set .owner to THIS_MODULE (2020-11-15 11:43:56 +0100)

are available in the Git repository at:

  git://git.open-mesh.org/linux-merge.git tags/batadv-net-pullrequest-20201127

for you to fetch changes up to 992b03b88e36254e26e9a4977ab948683e21bd9f:

  batman-adv: Don't always reallocate the fragmentation skb head (2020-11-27 08:02:55 +0100)

----------------------------------------------------------------
Here are some batman-adv bugfixes:

 - Fix head/tailroom issues for fragments, by Sven Eckelmann (3 patches)

----------------------------------------------------------------
Sven Eckelmann (3):
      batman-adv: Consider fragmentation for needed_headroom
      batman-adv: Reserve needed_*room for fragments
      batman-adv: Don't always reallocate the fragmentation skb head

 net/batman-adv/fragmentation.c  | 26 ++++++++++++++++----------
 net/batman-adv/hard-interface.c |  3 +++
 2 files changed, 19 insertions(+), 10 deletions(-)

[PATCH 1/3] batman-adv: Consider fragmentation for needed_headroom

[Simon Wunderlich]

From: Sven Eckelmann <sven@narfation.org>

If a batman-adv packets has to be fragmented, then the original batman-adv
packet header is not stripped away. Instead, only a new header is added in
front of the packet after it was split.

This size must be considered to avoid cost intensive reallocations during
the transmission through the various device layers.

Fixes: 7bca68c7844b ("batman-adv: Add lower layer needed_(head|tail)room to own ones")
Reported-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/hard-interface.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index dad99641df2a..33904595fc56 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -554,6 +554,9 @@ static void batadv_hardif_recalc_extra_skbroom(struct net_device *soft_iface)
 	needed_headroom = lower_headroom + (lower_header_len - ETH_HLEN);
 	needed_headroom += batadv_max_header_len();
 
+	/* fragmentation headers don't strip the unicast/... header */
+	needed_headroom += sizeof(struct batadv_frag_packet);
+
 	soft_iface->needed_headroom = needed_headroom;
 	soft_iface->needed_tailroom = lower_tailroom;
 }
-- 
2.20.1

[PATCH 2/3] batman-adv: Reserve needed_*room for fragments

[Simon Wunderlich]

From: Sven Eckelmann <sven@narfation.org>

The batadv net_device is trying to propagate the needed_headroom and
needed_tailroom from the lower devices. This is needed to avoid cost
intensive reallocations using pskb_expand_head during the transmission.

But the fragmentation code split the skb's without adding extra room at the
end/beginning of the various fragments. This reduced the performance of
transmissions over complex scenarios (batadv on vxlan on wireguard) because
the lower devices had to perform the reallocations at least once.

Fixes: ee75ed88879a ("batman-adv: Fragment and send skbs larger than mtu")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/fragmentation.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
index 9a47ef8b95c4..8de1fb567fd7 100644
--- a/net/batman-adv/fragmentation.c
+++ b/net/batman-adv/fragmentation.c
@@ -391,6 +391,7 @@ bool batadv_frag_skb_fwd(struct sk_buff *skb,
 
 /**
  * batadv_frag_create() - create a fragment from skb
+ * @net_dev: outgoing device for fragment
  * @skb: skb to create fragment from
  * @frag_head: header to use in new fragment
  * @fragment_size: size of new fragment
@@ -401,22 +402,25 @@ bool batadv_frag_skb_fwd(struct sk_buff *skb,
  *
  * Return: the new fragment, NULL on error.
  */
-static struct sk_buff *batadv_frag_create(struct sk_buff *skb,
+static struct sk_buff *batadv_frag_create(struct net_device *net_dev,
+					  struct sk_buff *skb,
 					  struct batadv_frag_packet *frag_head,
 					  unsigned int fragment_size)
 {
+	unsigned int ll_reserved = LL_RESERVED_SPACE(net_dev);
+	unsigned int tailroom = net_dev->needed_tailroom;
 	struct sk_buff *skb_fragment;
 	unsigned int header_size = sizeof(*frag_head);
 	unsigned int mtu = fragment_size + header_size;
 
-	skb_fragment = netdev_alloc_skb(NULL, mtu + ETH_HLEN);
+	skb_fragment = dev_alloc_skb(ll_reserved + mtu + tailroom);
 	if (!skb_fragment)
 		goto err;
 
 	skb_fragment->priority = skb->priority;
 
 	/* Eat the last mtu-bytes of the skb */
-	skb_reserve(skb_fragment, header_size + ETH_HLEN);
+	skb_reserve(skb_fragment, ll_reserved + header_size);
 	skb_split(skb, skb_fragment, skb->len - fragment_size);
 
 	/* Add the header */
@@ -439,11 +443,12 @@ int batadv_frag_send_packet(struct sk_buff *skb,
 			    struct batadv_orig_node *orig_node,
 			    struct batadv_neigh_node *neigh_node)
 {
+	struct net_device *net_dev = neigh_node->if_incoming->net_dev;
 	struct batadv_priv *bat_priv;
 	struct batadv_hard_iface *primary_if = NULL;
 	struct batadv_frag_packet frag_header;
 	struct sk_buff *skb_fragment;
-	unsigned int mtu = neigh_node->if_incoming->net_dev->mtu;
+	unsigned int mtu = net_dev->mtu;
 	unsigned int header_size = sizeof(frag_header);
 	unsigned int max_fragment_size, num_fragments;
 	int ret;
@@ -503,7 +508,7 @@ int batadv_frag_send_packet(struct sk_buff *skb,
 			goto put_primary_if;
 		}
 
-		skb_fragment = batadv_frag_create(skb, &frag_header,
+		skb_fragment = batadv_frag_create(net_dev, skb, &frag_header,
 						  max_fragment_size);
 		if (!skb_fragment) {
 			ret = -ENOMEM;
-- 
2.20.1

[PATCH 3/3] batman-adv: Don't always reallocate the fragmentation skb head

[Simon Wunderlich]

From: Sven Eckelmann <sven@narfation.org>

When a packet is fragmented by batman-adv, the original batman-adv header
is not modified. Only a new fragmentation is inserted between the original
one and the ethernet header. The code must therefore make sure that it has
a writable region of this size in the skbuff head.

But it is not useful to always reallocate the skbuff by this size even when
there would be more than enough headroom still in the skb. The reallocation
is just to costly during in this codepath.

Fixes: ee75ed88879a ("batman-adv: Fragment and send skbs larger than mtu")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/fragmentation.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
index 8de1fb567fd7..1f1f5b0873b2 100644
--- a/net/batman-adv/fragmentation.c
+++ b/net/batman-adv/fragmentation.c
@@ -527,13 +527,14 @@ int batadv_frag_send_packet(struct sk_buff *skb,
 		frag_header.no++;
 	}
 
-	/* Make room for the fragment header. */
-	if (batadv_skb_head_push(skb, header_size) < 0 ||
-	    pskb_expand_head(skb, header_size + ETH_HLEN, 0, GFP_ATOMIC) < 0) {
-		ret = -ENOMEM;
+	/* make sure that there is at least enough head for the fragmentation
+	 * and ethernet headers
+	 */
+	ret = skb_cow_head(skb, ETH_HLEN + header_size);
+	if (ret < 0)
 		goto put_primary_if;
-	}
 
+	skb_push(skb, header_size);
 	memcpy(skb->data, &frag_header, header_size);
 
 	/* Send the last fragment */
-- 
2.20.1

Re: [PATCH 0/3] pull request for net: batman-adv 2020-11-27

[Jakub Kicinski]

On Fri, 27 Nov 2020 18:38:46 +0100 Simon Wunderlich wrote:
> here are some more bugfixes for batman-adv which we would like to have integrated into net.
> 
> Please pull or let me know of any problem!> 
> ----------------------------------------------------------------
> Here are some batman-adv bugfixes:
> 
>  - Fix head/tailroom issues for fragments, by Sven Eckelmann (3 patches)

Pulled, thanks!