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packet: add PACKET_RESERVE sockopt 

Add new sockopt to reserve some headroom in the mmaped ring frames in
front of the packet payload. This can be used f.i. when the VLAN header
needs to be (re)constructed to avoid moving the entire payload.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Patrick McHardy 2008-07-18 18:05:19 -07:00 committed by David S. Miller
parent 3ca4095f24
commit 8913336a7e
2 changed files with 27 additions and 3 deletions
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1
include/linux/if_packet.h
View File

@ -45,6 +45,7 @@ struct sockaddr_ll
#define PACKET_ORIGDEV 9
#define PACKET_VERSION 10
#define PACKET_HDRLEN 11
#define PACKET_RESERVE 12
struct tpacket_stats
{

29
net/packet/af_packet.c
View File

@ -188,6 +188,7 @@ struct packet_sock {
unsigned int pg_vec_len;
enum tpacket_versions tp_version;
unsigned int tp_hdrlen;
unsigned int tp_reserve;
#endif
};
@ -635,11 +636,13 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
snaplen = res;
if (sk->sk_type == SOCK_DGRAM) {
macoff = netoff = TPACKET_ALIGN(po->tp_hdrlen) + 16;
macoff = netoff = TPACKET_ALIGN(po->tp_hdrlen) + 16 +
po->tp_reserve;
} else {
unsigned maclen = skb_network_offset(skb);
netoff = TPACKET_ALIGN(po->tp_hdrlen +
(maclen < 16 ? 16 : maclen));
(maclen < 16 ? 16 : maclen)) +
po->tp_reserve;
macoff = netoff - maclen;
}
@ -1448,6 +1451,19 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
return -EINVAL;
}
}
case PACKET_RESERVE:
{
unsigned int val;
if (optlen != sizeof(val))
return -EINVAL;
if (po->pg_vec)
return -EBUSY;
if (copy_from_user(&val, optval, sizeof(val)))
return -EFAULT;
po->tp_reserve = val;
return 0;
}
#endif
case PACKET_AUXDATA:
{
@ -1547,6 +1563,12 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
}
data = &val;
break;
case PACKET_RESERVE:
if (len > sizeof(unsigned int))
len = sizeof(unsigned int);
val = po->tp_reserve;
data = &val;
break;
#endif
default:
return -ENOPROTOOPT;
@ -1790,7 +1812,8 @@ static int packet_set_ring(struct sock *sk, struct tpacket_req *req, int closing
return -EINVAL;
if (unlikely(req->tp_block_size & (PAGE_SIZE - 1)))
return -EINVAL;
if (unlikely(req->tp_frame_size < po->tp_hdrlen))
if (unlikely(req->tp_frame_size < po->tp_hdrlen +
po->tp_reserve))
return -EINVAL;
if (unlikely(req->tp_frame_size & (TPACKET_ALIGNMENT - 1)))
return -EINVAL;