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[PACKET]: Add optional checksum computation for recvmsg 

This patch is needed to make ISC's DHCP server (and probably other
DHCP servers/clients using AF_PACKET) to be able to serve another
client on the same Xen host.

The problem is that packets between different domains on the same
Xen host only have partial checksums.  Unfortunately this piece of
information is not passed along in AF_PACKET unless you're using
the mmap interface.  Since dhcpd doesn't support packet-mmap, UDP
packets from the same host come out with apparently bogus checksums.

This patch adds a mechanism for AF_PACKET recvmsg(2) to return the
status along with the packet.  It does so by adding a new cmsg that
contains this information along with some other relevant data such
as the original packet length.

I didn't include the time stamp information since there is already
a cmsg for that.

This patch also changes the mmap code to set the CSUMNOTREADY flag
on all packets instead of just outoing packets on cooked sockets.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2007-02-04 23:31:32 -08:00 committed by David S. Miller
parent 8eb9086f21
commit 8dc4194474
2 changed files with 58 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
include/linux/if_packet.h
View File

@ -41,6 +41,7 @@ struct sockaddr_ll
#define PACKET_RX_RING 5
#define PACKET_STATISTICS 6
#define PACKET_COPY_THRESH 7
#define PACKET_AUXDATA 8
struct tpacket_stats
{
@ -48,6 +49,15 @@ struct tpacket_stats
unsigned int tp_drops;
};
struct tpacket_auxdata
{
__u32 tp_status;
__u32 tp_len;
__u32 tp_snaplen;
__u16 tp_mac;
__u16 tp_net;
};
struct tpacket_hdr
{
unsigned long tp_status;

57
net/packet/af_packet.c
View File

@ -200,7 +200,8 @@ struct packet_sock {
#endif
struct packet_type prot_hook;
spinlock_t bind_lock;
char running; /* prot_hook is attached*/
unsigned int running:1, /* prot_hook is attached*/
auxdata:1;
int ifindex; /* bound device */
__be16 num;
#ifdef CONFIG_PACKET_MULTICAST
@ -214,6 +215,8 @@ struct packet_sock {
#endif
};
#define PACKET_SKB_CB(__skb) ((struct tpacket_auxdata *)((__skb)->cb))
#ifdef CONFIG_PACKET_MMAP
static inline char *packet_lookup_frame(struct packet_sock *po, unsigned int position)
@ -462,6 +465,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev, struct packet
u8 * skb_head = skb->data;
int skb_len = skb->len;
unsigned int snaplen, res;
struct tpacket_auxdata *aux;
if (skb->pkt_type == PACKET_LOOPBACK)
goto drop;
@ -523,6 +527,15 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev, struct packet
if (dev->hard_header_parse)
sll->sll_halen = dev->hard_header_parse(skb, sll->sll_addr);
aux = PACKET_SKB_CB(skb);
aux->tp_status = TP_STATUS_USER;
if (skb->ip_summed == CHECKSUM_PARTIAL)
aux->tp_status |= TP_STATUS_CSUMNOTREADY;
aux->tp_len = skb->len;
aux->tp_snaplen = snaplen;
aux->tp_mac = 0;
aux->tp_net = skb->nh.raw - skb->data;
if (pskb_trim(skb, snaplen))
goto drop_n_acct;
@ -582,11 +595,12 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
else if (skb->pkt_type == PACKET_OUTGOING) {
/* Special case: outgoing packets have ll header at head */
skb_pull(skb, skb->nh.raw - skb->data);
if (skb->ip_summed == CHECKSUM_PARTIAL)
status |= TP_STATUS_CSUMNOTREADY;
}
}
if (skb->ip_summed == CHECKSUM_PARTIAL)
status |= TP_STATUS_CSUMNOTREADY;
snaplen = skb->len;
res = run_filter(skb, sk, snaplen);
@ -1119,6 +1133,11 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
if (msg->msg_name)
memcpy(msg->msg_name, skb->cb, msg->msg_namelen);
if (pkt_sk(sk)->auxdata) {
struct tpacket_auxdata *aux = PACKET_SKB_CB(skb);
put_cmsg(msg, SOL_PACKET, PACKET_AUXDATA, sizeof(*aux), aux);
}
/*
* Free or return the buffer as appropriate. Again this
* hides all the races and re-entrancy issues from us.
@ -1317,6 +1336,7 @@ static int
packet_setsockopt(struct socket *sock, int level, int optname, char __user *optval, int optlen)
{
struct sock *sk = sock->sk;
struct packet_sock *po = pkt_sk(sk);
int ret;
if (level != SOL_PACKET)
@ -1369,6 +1389,18 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
return 0;
}
#endif
case PACKET_AUXDATA:
{
int val;
if (optlen < sizeof(val))
return -EINVAL;
if (copy_from_user(&val, optval, sizeof(val)))
return -EFAULT;
po->auxdata = !!val;
return 0;
}
default:
return -ENOPROTOOPT;
}
@ -1378,8 +1410,11 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
char __user *optval, int __user *optlen)
{
int len;
int val;
struct sock *sk = sock->sk;
struct packet_sock *po = pkt_sk(sk);
void *data;
struct tpacket_stats st;
if (level != SOL_PACKET)
return -ENOPROTOOPT;
@ -1392,9 +1427,6 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
switch(optname) {
case PACKET_STATISTICS:
{
struct tpacket_stats st;
if (len > sizeof(struct tpacket_stats))
len = sizeof(struct tpacket_stats);
spin_lock_bh(&sk->sk_receive_queue.lock);
@ -1403,16 +1435,23 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
spin_unlock_bh(&sk->sk_receive_queue.lock);
st.tp_packets += st.tp_drops;
if (copy_to_user(optval, &st, len))
return -EFAULT;
data = &st;
break;
case PACKET_AUXDATA:
if (len > sizeof(int))
len = sizeof(int);
val = po->auxdata;
data = &val;
break;
}
default:
return -ENOPROTOOPT;
}
if (put_user(len, optlen))
return -EFAULT;
if (copy_to_user(optval, data, len))
return -EFAULT;
return 0;
}