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 <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index db792e0..de73bcb 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -188,6 +188,7 @@
unsigned int pg_vec_len;
enum tpacket_versions tp_version;
unsigned int tp_hdrlen;
+ unsigned int tp_reserve;
#endif
};
@@ -635,11 +636,13 @@
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 @@
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 @@
}
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 @@
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;
