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Commit 2472d761 authored by Eyal Birger's avatar Eyal Birger Committed by David S. Miller
Browse files

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



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: default avatarEyal Birger <eyal.birger@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2cfdf9fc

net/packet/af_packet.c

+24 −6
Original line number Diff line number Diff line
@@ -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;

		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);