[B.A.T.M.A.N.] [RFCv2 1/4] batman-adv: Reserve extra bytes in skb for better alignment

[Sven Eckelmann <sven@narfation.org>]

The ethernet header is 14 bytes long. Therefore, the data after it is not 4
byte aligned and may cause problems on systems without unaligned data access.
Reserving NET_IP_ALIGN more byes can fix the misalignment of the ethernet
header.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
Oops, the allocation of the skb also has to be changed

 bat_iv_ogm.c        |    8 +++++---
 icmp_socket.c       |    4 ++--
 translation-table.c |   20 ++++++++++----------
 vis.c               |    9 +++++----
 4 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c
index 75403a4..9f3925a 100644
--- a/bat_iv_ogm.c
+++ b/bat_iv_ogm.c
@@ -411,9 +411,11 @@ static void batadv_iv_ogm_aggregate_new(const unsigned char *packet_buff,
 
 	if ((atomic_read(&bat_priv->aggregated_ogms)) &&
 	    (packet_len < BATADV_MAX_AGGREGATION_BYTES))
-		skb_size = BATADV_MAX_AGGREGATION_BYTES + ETH_HLEN;
+		skb_size = BATADV_MAX_AGGREGATION_BYTES;
 	else
-		skb_size = packet_len + ETH_HLEN;
+		skb_size = packet_len;
+
+	skb_size += ETH_HLEN + NET_IP_ALIGN;
 
 	forw_packet_aggr->skb = dev_alloc_skb(skb_size);
 	if (!forw_packet_aggr->skb) {
@@ -422,7 +424,7 @@ static void batadv_iv_ogm_aggregate_new(const unsigned char *packet_buff,
 		kfree(forw_packet_aggr);
 		goto out;
 	}
-	skb_reserve(forw_packet_aggr->skb, ETH_HLEN);
+	skb_reserve(forw_packet_aggr->skb, ETH_HLEN + NET_IP_ALIGN);
 
 	INIT_HLIST_NODE(&forw_packet_aggr->list);
 
diff --git a/icmp_socket.c b/icmp_socket.c
index 5874c0e..87ca809 100644
--- a/icmp_socket.c
+++ b/icmp_socket.c
@@ -177,13 +177,13 @@ static ssize_t batadv_socket_write(struct file *file, const char __user *buff,
 	if (len >= sizeof(struct batadv_icmp_packet_rr))
 		packet_len = sizeof(struct batadv_icmp_packet_rr);
 
-	skb = dev_alloc_skb(packet_len + ETH_HLEN);
+	skb = dev_alloc_skb(packet_len + ETH_HLEN + NET_IP_ALIGN);
 	if (!skb) {
 		len = -ENOMEM;
 		goto out;
 	}
 
-	skb_reserve(skb, ETH_HLEN);
+	skb_reserve(skb, ETH_HLEN + NET_IP_ALIGN);
 	icmp_packet = (struct batadv_icmp_packet_rr *)skb_put(skb, packet_len);
 
 	if (copy_from_user(icmp_packet, buff, packet_len)) {
diff --git a/translation-table.c b/translation-table.c
index 6fecb94..c731050 100644
--- a/translation-table.c
+++ b/translation-table.c
@@ -1594,11 +1594,11 @@ batadv_tt_response_fill_table(uint16_t tt_len, uint8_t ttvn,
 	tt_tot = tt_len / sizeof(struct batadv_tt_change);
 
 	len = tt_query_size + tt_len;
-	skb = dev_alloc_skb(len + ETH_HLEN);
+	skb = dev_alloc_skb(len + ETH_HLEN + NET_IP_ALIGN);
 	if (!skb)
 		goto out;
 
-	skb_reserve(skb, ETH_HLEN);
+	skb_reserve(skb, ETH_HLEN + NET_IP_ALIGN);
 	tt_response = (struct batadv_tt_query_packet *)skb_put(skb, len);
 	tt_response->ttvn = ttvn;
 
@@ -1659,11 +1659,11 @@ static int batadv_send_tt_request(struct batadv_priv *bat_priv,
 	if (!tt_req_node)
 		goto out;
 
-	skb = dev_alloc_skb(sizeof(*tt_request) + ETH_HLEN);
+	skb = dev_alloc_skb(sizeof(*tt_request) + ETH_HLEN + NET_IP_ALIGN);
 	if (!skb)
 		goto out;
 
-	skb_reserve(skb, ETH_HLEN);
+	skb_reserve(skb, ETH_HLEN + NET_IP_ALIGN);
 
 	tt_req_len = sizeof(*tt_request);
 	tt_request = (struct batadv_tt_query_packet *)skb_put(skb, tt_req_len);
@@ -1761,11 +1761,11 @@ batadv_send_other_tt_response(struct batadv_priv *bat_priv,
 		tt_tot = tt_len / sizeof(struct batadv_tt_change);
 
 		len = sizeof(*tt_response) + tt_len;
-		skb = dev_alloc_skb(len + ETH_HLEN);
+		skb = dev_alloc_skb(len + ETH_HLEN + NET_IP_ALIGN);
 		if (!skb)
 			goto unlock;
 
-		skb_reserve(skb, ETH_HLEN);
+		skb_reserve(skb, ETH_HLEN + NET_IP_ALIGN);
 		packet_pos = skb_put(skb, len);
 		tt_response = (struct batadv_tt_query_packet *)packet_pos;
 		tt_response->ttvn = req_ttvn;
@@ -1880,11 +1880,11 @@ batadv_send_my_tt_response(struct batadv_priv *bat_priv,
 		tt_tot = tt_len / sizeof(struct batadv_tt_change);
 
 		len = sizeof(*tt_response) + tt_len;
-		skb = dev_alloc_skb(len + ETH_HLEN);
+		skb = dev_alloc_skb(len + ETH_HLEN + NET_IP_ALIGN);
 		if (!skb)
 			goto unlock;
 
-		skb_reserve(skb, ETH_HLEN);
+		skb_reserve(skb, ETH_HLEN + NET_IP_ALIGN);
 		packet_pos = skb_put(skb, len);
 		tt_response = (struct batadv_tt_query_packet *)packet_pos;
 		tt_response->ttvn = req_ttvn;
@@ -2211,11 +2211,11 @@ static void batadv_send_roam_adv(struct batadv_priv *bat_priv, uint8_t *client,
 	if (!batadv_tt_check_roam_count(bat_priv, client))
 		goto out;
 
-	skb = dev_alloc_skb(sizeof(*roam_adv_packet) + ETH_HLEN);
+	skb = dev_alloc_skb(sizeof(*roam_adv_packet) + ETH_HLEN + NET_IP_ALIGN);
 	if (!skb)
 		goto out;
 
-	skb_reserve(skb, ETH_HLEN);
+	skb_reserve(skb, ETH_HLEN + NET_IP_ALIGN);
 
 	roam_adv_packet = (struct batadv_roam_adv_packet *)skb_put(skb, len);
 
diff --git a/vis.c b/vis.c
index 79589a3..0f65a9d 100644
--- a/vis.c
+++ b/vis.c
@@ -396,12 +396,12 @@ batadv_add_packet(struct batadv_priv *bat_priv,
 		return NULL;
 
 	len = sizeof(*packet) + vis_info_len;
-	info->skb_packet = dev_alloc_skb(len + ETH_HLEN);
+	info->skb_packet = dev_alloc_skb(len + ETH_HLEN + NET_IP_ALIGN);
 	if (!info->skb_packet) {
 		kfree(info);
 		return NULL;
 	}
-	skb_reserve(info->skb_packet, ETH_HLEN);
+	skb_reserve(info->skb_packet, ETH_HLEN + NET_IP_ALIGN);
 	packet = (struct batadv_vis_packet *)skb_put(info->skb_packet, len);
 
 	kref_init(&info->refcount);
@@ -856,12 +856,13 @@ int batadv_vis_init(struct batadv_priv *bat_priv)
 	if (!bat_priv->vis.my_info)
 		goto err;
 
-	len = sizeof(*packet) + BATADV_MAX_VIS_PACKET_SIZE + ETH_HLEN;
+	len = sizeof(*packet) + BATADV_MAX_VIS_PACKET_SIZE;
+	len += ETH_HLEN + NET_IP_ALIGN;
 	bat_priv->vis.my_info->skb_packet = dev_alloc_skb(len);
 	if (!bat_priv->vis.my_info->skb_packet)
 		goto free_info;
 
-	skb_reserve(bat_priv->vis.my_info->skb_packet, ETH_HLEN);
+	skb_reserve(bat_priv->vis.my_info->skb_packet, ETH_HLEN + NET_IP_ALIGN);
 	tmp_skb = bat_priv->vis.my_info->skb_packet;
 	packet = (struct batadv_vis_packet *)skb_put(tmp_skb, sizeof(*packet));
 
-- 
1.7.10.4