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net: packet: use sockaddr_ll fields as storage for skb original length in recvmsg path

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As part of an effort to move skb->dropcount to skb->cb[], 4 bytes
of additional room are needed in skb->cb[] in packet sockets.

Store the skb original length in the first two fields of sockaddr_ll
(sll_family and sll_protocol) as they can be derived from the skb when
needed.

Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eyal Birger 2015-03-01 14:58:28 +02:00 committed by David S. Miller
parent 2cfdf9fcb8
commit 2472d7613b
1 changed files with 24 additions and 6 deletions
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30
net/packet/af_packet.c
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@ -216,10 +216,16 @@ static void prb_fill_vlan_info(struct tpacket_kbdq_core *,
static void packet_flush_mclist(struct sock *sk);
struct packet_skb_cb {
unsigned int origlen;
union {
struct sockaddr_pkt pkt;
struct sockaddr_ll ll;
union {
/* Trick: alias skb original length with
* ll.sll_family and ll.protocol in order
* to save room.
*/
unsigned int origlen;
struct sockaddr_ll ll;
};
} sa;
};
@ -1814,9 +1820,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
sizeof(skb->cb));
sll = &PACKET_SKB_CB(skb)->sa.ll;
sll->sll_family = AF_PACKET;
sll->sll_hatype = dev->type;
sll->sll_protocol = skb->protocol;
sll->sll_pkttype = skb->pkt_type;
if (unlikely(po->origdev))
sll->sll_ifindex = orig_dev->ifindex;
@ -1825,7 +1829,10 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
sll->sll_halen = dev_parse_header(skb, sll->sll_addr);
PACKET_SKB_CB(skb)->origlen = skb->len;
/* sll->sll_family and sll->sll_protocol are set in packet_recvmsg().
* Use their space for storing the original skb length.
*/
PACKET_SKB_CB(skb)->sa.origlen = skb->len;
if (pskb_trim(skb, snaplen))
goto drop_n_acct;
@ -2883,6 +2890,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
struct sk_buff *skb;
int copied, err;
int vnet_hdr_len = 0;
unsigned int origlen = 0;
err = -EINVAL;
if (flags & ~(MSG_PEEK|MSG_DONTWAIT|MSG_TRUNC|MSG_CMSG_COMPAT|MSG_ERRQUEUE))
@ -2982,6 +2990,15 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
if (err)
goto out_free;
if (sock->type != SOCK_PACKET) {
struct sockaddr_ll *sll = &PACKET_SKB_CB(skb)->sa.ll;
/* Original length was stored in sockaddr_ll fields */
origlen = PACKET_SKB_CB(skb)->sa.origlen;
sll->sll_family = AF_PACKET;
sll->sll_protocol = skb->protocol;
}
sock_recv_ts_and_drops(msg, sk, skb);
if (msg->msg_name) {
@ -2993,6 +3010,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
msg->msg_namelen = sizeof(struct sockaddr_pkt);
} else {
struct sockaddr_ll *sll = &PACKET_SKB_CB(skb)->sa.ll;
msg->msg_namelen = sll->sll_halen +
offsetof(struct sockaddr_ll, sll_addr);
}
@ -3006,7 +3024,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
aux.tp_status = TP_STATUS_USER;
if (skb->ip_summed == CHECKSUM_PARTIAL)
aux.tp_status |= TP_STATUS_CSUMNOTREADY;
aux.tp_len = PACKET_SKB_CB(skb)->origlen;
aux.tp_len = origlen;
aux.tp_snaplen = skb->len;
aux.tp_mac = 0;
aux.tp_net = skb_network_offset(skb);