diff --git a/Documentation/DocBook/mac80211.tmpl b/Documentation/DocBook/mac80211.tmpl
index 77c3c202991b4ded85f4795ef33e3e73186dd784..bdf908a6e545b1f10e3cc16d2130d9540c06dab4 100644
--- a/Documentation/DocBook/mac80211.tmpl
+++ b/Documentation/DocBook/mac80211.tmpl
@@ -165,8 +165,8 @@ usage should require reading the full document.
!Pinclude/net/mac80211.h Frame format
- Alignment issues
- TBD
+ Packet alignment
+!Pnet/mac80211/rx.c Packet alignment
Calling into mac80211 from interrupts
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index ddb966f5888217ce23cdbc6fed120ba6ba628697..b68e082e99cea7710f6ceae76453fb84c84bf3bc 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -102,7 +102,7 @@ ieee80211_rx_radiotap_len(struct ieee80211_local *local,
return len;
}
-/**
+/*
* ieee80211_add_rx_radiotap_header - add radiotap header
*
* add a radiotap header containing all the fields which the hardware provided.
@@ -371,39 +371,50 @@ static void ieee80211_parse_qos(struct ieee80211_rx_data *rx)
rx->skb->priority = (tid > 7) ? 0 : tid;
}
-static void ieee80211_verify_ip_alignment(struct ieee80211_rx_data *rx)
+/**
+ * DOC: Packet alignment
+ *
+ * Drivers always need to pass packets that are aligned to two-byte boundaries
+ * to the stack.
+ *
+ * Additionally, should, if possible, align the payload data in a way that
+ * guarantees that the contained IP header is aligned to a four-byte
+ * boundary. In the case of regular frames, this simply means aligning the
+ * payload to a four-byte boundary (because either the IP header is directly
+ * contained, or IV/RFC1042 headers that have a length divisible by four are
+ * in front of it).
+ *
+ * With A-MSDU frames, however, the payload data address must yield two modulo
+ * four because there are 14-byte 802.3 headers within the A-MSDU frames that
+ * push the IP header further back to a multiple of four again. Thankfully, the
+ * specs were sane enough this time around to require padding each A-MSDU
+ * subframe to a length that is a multiple of four.
+ *
+ * Padding like Atheros hardware adds which is inbetween the 802.11 header and
+ * the payload is not supported, the driver is required to move the 802.11
+ * header to be directly in front of the payload in that case.
+ */
+static void ieee80211_verify_alignment(struct ieee80211_rx_data *rx)
{
-#ifdef CONFIG_MAC80211_DEBUG_PACKET_ALIGNMENT
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
int hdrlen;
+#ifndef CONFIG_MAC80211_DEBUG_PACKET_ALIGNMENT
+ return;
+#endif
+
+ if (WARN_ONCE((unsigned long)rx->skb->data & 1,
+ "unaligned packet at 0x%p\n", rx->skb->data))
+ return;
+
if (!ieee80211_is_data_present(hdr->frame_control))
return;
- /*
- * Drivers are required to align the payload data in a way that
- * guarantees that the contained IP header is aligned to a four-
- * byte boundary. In the case of regular frames, this simply means
- * aligning the payload to a four-byte boundary (because either
- * the IP header is directly contained, or IV/RFC1042 headers that
- * have a length divisible by four are in front of it.
- *
- * With A-MSDU frames, however, the payload data address must
- * yield two modulo four because there are 14-byte 802.3 headers
- * within the A-MSDU frames that push the IP header further back
- * to a multiple of four again. Thankfully, the specs were sane
- * enough this time around to require padding each A-MSDU subframe
- * to a length that is a multiple of four.
- *
- * Padding like atheros hardware adds which is inbetween the 802.11
- * header and the payload is not supported, the driver is required
- * to move the 802.11 header further back in that case.
- */
hdrlen = ieee80211_hdrlen(hdr->frame_control);
if (rx->flags & IEEE80211_RX_AMSDU)
hdrlen += ETH_HLEN;
- WARN_ON_ONCE(((unsigned long)(rx->skb->data + hdrlen)) & 3);
-#endif
+ WARN_ONCE(((unsigned long)(rx->skb->data + hdrlen)) & 3,
+ "unaligned IP payload at 0x%p\n", rx->skb->data + hdrlen);
}
@@ -1267,10 +1278,37 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
}
if (skb) {
- /* deliver to local stack */
- skb->protocol = eth_type_trans(skb, dev);
- memset(skb->cb, 0, sizeof(skb->cb));
- netif_rx(skb);
+ int align __maybe_unused;
+
+#if defined(CONFIG_MAC80211_DEBUG_PACKET_ALIGNMENT) || !defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
+ /*
+ * 'align' will only take the values 0 or 2 here
+ * since all frames are required to be aligned
+ * to 2-byte boundaries when being passed to
+ * mac80211. That also explains the __skb_push()
+ * below.
+ */
+ align = (unsigned long)skb->data & 4;
+ if (align) {
+ if (WARN_ON(skb_headroom(skb) < 3)) {
+ dev_kfree_skb(skb);
+ skb = NULL;
+ } else {
+ u8 *data = skb->data;
+ size_t len = skb->len;
+ u8 *new = __skb_push(skb, align);
+ memmove(new, data, len);
+ __skb_trim(skb, len);
+ }
+ }
+#endif
+
+ if (skb) {
+ /* deliver to local stack */
+ skb->protocol = eth_type_trans(skb, dev);
+ memset(skb->cb, 0, sizeof(skb->cb));
+ netif_rx(skb);
+ }
}
if (xmit_skb) {
@@ -1339,14 +1377,20 @@ ieee80211_rx_h_amsdu(struct ieee80211_rx_data *rx)
if (remaining <= subframe_len + padding)
frame = skb;
else {
- frame = dev_alloc_skb(local->hw.extra_tx_headroom +
- subframe_len);
+ /*
+ * Allocate and reserve two bytes more for payload
+ * alignment since sizeof(struct ethhdr) is 14.
+ */
+ frame = dev_alloc_skb(
+ ALIGN(local->hw.extra_tx_headroom, 4) +
+ subframe_len + 2);
if (frame == NULL)
return RX_DROP_UNUSABLE;
- skb_reserve(frame, local->hw.extra_tx_headroom +
- sizeof(struct ethhdr));
+ skb_reserve(frame,
+ ALIGN(local->hw.extra_tx_headroom, 4) +
+ sizeof(struct ethhdr) + 2);
memcpy(skb_put(frame, ntohs(len)), skb->data,
ntohs(len));
@@ -1976,7 +2020,7 @@ static void __ieee80211_rx_handle_packet(struct ieee80211_hw *hw,
rx.flags |= IEEE80211_RX_IN_SCAN;
ieee80211_parse_qos(&rx);
- ieee80211_verify_ip_alignment(&rx);
+ ieee80211_verify_alignment(&rx);
skb = rx.skb;