From 60659b2d9eac5c726d4f25c2cfb2eea6821651f2 Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Mon, 18 Mar 2019 12:59:20 +0100
Subject: mac80211: optimize skb resizing to avoid reallocation when using
802.11s + batman-adv
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
.../357-mac80211-optimize-skb-resizing.patch | 198 +++++++++++++++++++++
1 file changed, 198 insertions(+)
create mode 100644 package/kernel/mac80211/patches/subsys/357-mac80211-optimize-skb-resizing.patch
(limited to 'package/kernel/mac80211')
diff --git a/package/kernel/mac80211/patches/subsys/357-mac80211-optimize-skb-resizing.patch b/package/kernel/mac80211/patches/subsys/357-mac80211-optimize-skb-resizing.patch
new file mode 100644
index 0000000000..8fd85fedcc
--- /dev/null
+++ b/package/kernel/mac80211/patches/subsys/357-mac80211-optimize-skb-resizing.patch
@@ -0,0 +1,198 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Sun, 17 Mar 2019 18:11:30 +0100
+Subject: [PATCH] mac80211: optimize skb resizing
+
+When forwarding unicast packets from ethernet to batman-adv over 802.11s
+(with forwarding disabled), the typical required headroom to transmit
+encrypted packets on mt76 is 32 (802.11) + 6 (802.11s) + 8 (CCMP) +
+2 (padding) + 6 (LLC) + 18 (batman-adv) - 14 (old ethernet header) = 58 bytes.
+
+On systems where NET_SKB_PAD is 64 this leads to a call to pskb_expand_head
+for every packet, since mac80211 also tries to allocate 16 bytes status
+headroom for radiotap headers.
+
+This patch fixes these unnecessary reallocations by only requiring the extra
+status headroom in ieee80211_tx_monitor()
+If however a reallocation happens before that call, the status headroom gets
+added there as well, in order to avoid double reallocation.
+
+The patch also cleans up the code by moving the headroom calculation to
+ieee80211_skb_resize.
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/mac80211/ieee80211_i.h
++++ b/net/mac80211/ieee80211_i.h
+@@ -1761,6 +1761,8 @@ void ieee80211_clear_fast_xmit(struct st
+ int ieee80211_tx_control_port(struct wiphy *wiphy, struct net_device *dev,
+ const u8 *buf, size_t len,
+ const u8 *dest, __be16 proto, bool unencrypted);
++int ieee80211_skb_resize(struct ieee80211_sub_if_data *sdata,
++ struct sk_buff *skb, int hdrlen, int hdr_add);
+
+ /* HT */
+ void ieee80211_apply_htcap_overrides(struct ieee80211_sub_if_data *sdata,
+--- a/net/mac80211/status.c
++++ b/net/mac80211/status.c
+@@ -672,6 +672,11 @@ void ieee80211_tx_monitor(struct ieee802
+ }
+ }
+
++ if (ieee80211_skb_resize(NULL, skb, 0, 0)) {
++ dev_kfree_skb(skb);
++ return;
++ }
++
+ /* send frame to monitor interfaces now */
+ rtap_len = ieee80211_tx_radiotap_len(info);
+ if (WARN_ON_ONCE(skb_headroom(skb) < rtap_len)) {
+--- a/net/mac80211/tx.c
++++ b/net/mac80211/tx.c
+@@ -1914,37 +1914,53 @@ static bool ieee80211_tx(struct ieee8021
+ }
+
+ /* device xmit handlers */
+-
+-static int ieee80211_skb_resize(struct ieee80211_sub_if_data *sdata,
+- struct sk_buff *skb,
+- int head_need, bool may_encrypt)
++int ieee80211_skb_resize(struct ieee80211_sub_if_data *sdata,
++ struct sk_buff *skb, int hdr_len, int hdr_extra)
+ {
+ struct ieee80211_local *local = sdata->local;
++ struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+ struct ieee80211_hdr *hdr;
+- bool enc_tailroom;
+- int tail_need = 0;
++ int head_need, head_max;
++ int tail_need, tail_max;
++ bool enc_tailroom = false;
+
+- hdr = (struct ieee80211_hdr *) skb->data;
+- enc_tailroom = may_encrypt &&
+- (sdata->crypto_tx_tailroom_needed_cnt ||
+- ieee80211_is_mgmt(hdr->frame_control));
++ if (sdata && !hdr_len &&
++ !(info->flags & IEEE80211_TX_INTFL_DONT_ENCRYPT)) {
++ hdr = (struct ieee80211_hdr *) skb->data;
++ enc_tailroom = (sdata->crypto_tx_tailroom_needed_cnt ||
++ ieee80211_is_mgmt(hdr->frame_control));
++ hdr_len += sdata->encrypt_headroom;
++ }
+
+- if (enc_tailroom) {
+- tail_need = IEEE80211_ENCRYPT_TAILROOM;
+- tail_need -= skb_tailroom(skb);
+- tail_need = max_t(int, tail_need, 0);
++ head_need = head_max = hdr_len;
++ tail_need = tail_max = 0;
++ if (!sdata) {
++ head_need = head_max = local->tx_headroom;
++ } else {
++ head_max += hdr_extra;
++ head_max += max_t(int, local->tx_headroom,
++ local->hw.extra_tx_headroom);
++ head_need += local->hw.extra_tx_headroom;
++
++ tail_max = IEEE80211_ENCRYPT_TAILROOM;
++ if (enc_tailroom)
++ tail_need = tail_max;
+ }
+
+ if (skb_cloned(skb) &&
+ (!ieee80211_hw_check(&local->hw, SUPPORTS_CLONED_SKBS) ||
+ !skb_clone_writable(skb, ETH_HLEN) || enc_tailroom))
+ I802_DEBUG_INC(local->tx_expand_skb_head_cloned);
+- else if (head_need || tail_need)
++ else if (head_need > skb_headroom(skb) ||
++ tail_need > skb_tailroom(skb))
+ I802_DEBUG_INC(local->tx_expand_skb_head);
+ else
+ return 0;
+
+- if (pskb_expand_head(skb, head_need, tail_need, GFP_ATOMIC)) {
++ head_max = max_t(int, 0, head_max - skb_headroom(skb));
++ tail_max = max_t(int, 0, tail_max - skb_tailroom(skb));
++
++ if (pskb_expand_head(skb, head_max, tail_max, GFP_ATOMIC)) {
+ wiphy_debug(local->hw.wiphy,
+ "failed to reallocate TX buffer\n");
+ return -ENOMEM;
+@@ -1960,18 +1976,8 @@ void ieee80211_xmit(struct ieee80211_sub
+ struct ieee80211_local *local = sdata->local;
+ struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+ struct ieee80211_hdr *hdr;
+- int headroom;
+- bool may_encrypt;
+-
+- may_encrypt = !(info->flags & IEEE80211_TX_INTFL_DONT_ENCRYPT);
+-
+- headroom = local->tx_headroom;
+- if (may_encrypt)
+- headroom += sdata->encrypt_headroom;
+- headroom -= skb_headroom(skb);
+- headroom = max_t(int, 0, headroom);
+
+- if (ieee80211_skb_resize(sdata, skb, headroom, may_encrypt)) {
++ if (ieee80211_skb_resize(sdata, skb, 0, 0)) {
+ ieee80211_free_txskb(&local->hw, skb);
+ return;
+ }
+@@ -2740,30 +2746,14 @@ static struct sk_buff *ieee80211_build_h
+
+ skb_pull(skb, skip_header_bytes);
+ padsize = ieee80211_hdr_padsize(&local->hw, hdrlen);
+- head_need = hdrlen + encaps_len + meshhdrlen - skb_headroom(skb);
++ head_need = hdrlen + encaps_len + meshhdrlen;
+ head_need += padsize;
+
+- /*
+- * So we need to modify the skb header and hence need a copy of
+- * that. The head_need variable above doesn't, so far, include
+- * the needed header space that we don't need right away. If we
+- * can, then we don't reallocate right now but only after the
+- * frame arrives at the master device (if it does...)
+- *
+- * If we cannot, however, then we will reallocate to include all
+- * the ever needed space. Also, if we need to reallocate it anyway,
+- * make it big enough for everything we may ever need.
+- */
+-
+- if (head_need > 0 || skb_cloned(skb)) {
+- head_need += sdata->encrypt_headroom;
+- head_need += local->tx_headroom;
+- head_need = max_t(int, 0, head_need);
+- if (ieee80211_skb_resize(sdata, skb, head_need, true)) {
+- ieee80211_free_txskb(&local->hw, skb);
+- skb = NULL;
+- return ERR_PTR(-ENOMEM);
+- }
++ if (ieee80211_skb_resize(sdata, skb, head_need,
++ sdata->encrypt_headroom)) {
++ ieee80211_free_txskb(&local->hw, skb);
++ skb = NULL;
++ return ERR_PTR(-ENOMEM);
+ }
+
+ if (encaps_data)
+@@ -3377,7 +3367,6 @@ static bool ieee80211_xmit_fast(struct i
+ struct ieee80211_local *local = sdata->local;
+ u16 ethertype = (skb->data[12] << 8) | skb->data[13];
+ int extra_head = fast_tx->hdr_len - (ETH_HLEN - 2);
+- int hw_headroom = sdata->local->hw.extra_tx_headroom;
+ struct ethhdr eth;
+ struct ieee80211_tx_info *info;
+ struct ieee80211_hdr *hdr = (void *)fast_tx->hdr;
+@@ -3429,10 +3418,7 @@ static bool ieee80211_xmit_fast(struct i
+ * as the may-encrypt argument for the resize to not account for
+ * more room than we already have in 'extra_head'
+ */
+- if (unlikely(ieee80211_skb_resize(sdata, skb,
+- max_t(int, extra_head + hw_headroom -
+- skb_headroom(skb), 0),
+- false))) {
++ if (unlikely(ieee80211_skb_resize(sdata, skb, extra_head, 0))) {
+ kfree_skb(skb);
+ return true;
+ }
--
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