diff options
| -rw-r--r-- | Documentation/DocBook/mac80211.tmpl | 4 | ||||
| -rw-r--r-- | net/mac80211/rx.c | 110 |
2 files changed, 79 insertions, 35 deletions
diff --git a/Documentation/DocBook/mac80211.tmpl b/Documentation/DocBook/mac80211.tmpl index 77c3c20..bdf908a 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 </sect1> <sect1> - <title>Alignment issues</title> - <para>TBD</para> + <title>Packet alignment</title> +!Pnet/mac80211/rx.c Packet alignment </sect1> <sect1> <title>Calling into mac80211 from interrupts</title> diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c index ddb966f..b68e082 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; |
