@@ -163,6 +163,19 @@ As capture, each frame contains two parts:
A complete tutorial is available at: http://wiki.gnu-log.net/
+By default, the user should put data at :
+ frame base + TPACKET_HDRLEN - sizeof(struct sockaddr_ll)
+
+So, whatever you choose for the socket mode (SOCK_DGRAM or SOCK_RAW),
+the beginning of the user data will be at :
+ frame base + TPACKET_ALIGN(sizeof(struct tpacket_hdr))
+
+If you wish to put user data at a custom offset from the beginning of
+the frame (for payload alignment with SOCK_RAW mode for instance) you
+can set tp_net (with SOCK_DGRAM) or tp_mac (with SOCK_RAW). In order
+to make this work it must be enabled previously with setsockopt()
+and the PACKET_TX_HAS_OFF option.
+
--------------------------------------------------------------------------------
+ PACKET_MMAP settings
--------------------------------------------------------------------------------
@@ -50,6 +50,7 @@ struct sockaddr_ll {
#define PACKET_TX_TIMESTAMP 16
#define PACKET_TIMESTAMP 17
#define PACKET_FANOUT 18
+#define PACKET_TX_HAS_OFF 19
#define PACKET_FANOUT_HASH 0
#define PACKET_FANOUT_LB 1
@@ -1881,7 +1881,35 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
skb_reserve(skb, hlen);
skb_reset_network_header(skb);
- data = ph.raw + po->tp_hdrlen - sizeof(struct sockaddr_ll);
+ if (po->tp_tx_has_off) {
+ int off_min, off_max, off;
+ off_min = po->tp_hdrlen - sizeof(struct sockaddr_ll);
+ off_max = po->tx_ring.frame_size - tp_len;
+ if (sock->type == SOCK_DGRAM) {
+ switch (po->tp_version) {
+ case TPACKET_V2:
+ off = ph.h2->tp_net;
+ break;
+ default:
+ off = ph.h1->tp_net;
+ break;
+ }
+ } else {
+ switch (po->tp_version) {
+ case TPACKET_V2:
+ off = ph.h2->tp_mac;
+ break;
+ default:
+ off = ph.h1->tp_mac;
+ break;
+ }
+ }
+ if (unlikely((off < off_min) || (off_max < off)))
+ return -EINVAL;
+ data = ph.raw + off;
+ } else {
+ data = ph.raw + po->tp_hdrlen - sizeof(struct sockaddr_ll);
+ }
to_write = tp_len;
if (sock->type == SOCK_DGRAM) {
@@ -3109,6 +3137,19 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
return fanout_add(sk, val & 0xffff, val >> 16);
}
+ case PACKET_TX_HAS_OFF:
+ {
+ unsigned int val;
+
+ if (optlen != sizeof(val))
+ return -EINVAL;
+ if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
+ return -EBUSY;
+ if (copy_from_user(&val, optval, sizeof(val)))
+ return -EFAULT;
+ po->tp_tx_has_off = !!val;
+ return 0;
+ }
default:
return -ENOPROTOOPT;
}
@@ -3200,6 +3241,9 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
((u32)po->fanout->type << 16)) :
0);
break;
+ case PACKET_TX_HAS_OFF:
+ val = po->tp_tx_has_off;
+ break;
default:
return -ENOPROTOOPT;
}
@@ -109,6 +109,7 @@ struct packet_sock {
unsigned int tp_hdrlen;
unsigned int tp_reserve;
unsigned int tp_loss:1;
+ unsigned int tp_tx_has_off:1;
unsigned int tp_tstamp;
struct packet_type prot_hook ____cacheline_aligned_in_smp;
};
The tx data offset of packet mmap tx ring used to be : (TPACKET2_HDRLEN - sizeof(struct sockaddr_ll)) The problem is that, with SOCK_RAW socket, the payload (14 bytes after the beginning of the user data) is misaligned. This patch allows to let the user gives an offset for it's tx data if he desires. Set sock option PACKET_TX_HAS_OFF to 1, then specify in each frame of your tx ring tp_net for SOCK_DGRAM, or tp_mac for SOCK_RAW. Signed-off-by: Paul Chavent <paul.chavent@onera.fr> --- Documentation/networking/packet_mmap.txt | 13 +++++++++ include/uapi/linux/if_packet.h | 1 + net/packet/af_packet.c | 46 +++++++++++++++++++++++++++++++- net/packet/internal.h | 1 + 4 files changed, 60 insertions(+), 1 deletion(-)