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Date: Wed, 24 Jan 2007 10:38:34 +1100
From: Herbert Xu <herbert@...dor.apana.org.au>
To: "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PACKET]: Add PACKET_AUXDATA cmsg
On Wed, Jan 10, 2007 at 01:54:35PM +1100, Herbert Xu wrote:
>
> [PACKET]: Add optional checksum computation for recvmsg
Unfortunately I missed the fact the skb->cb is already used to store
the sockaddr. This patch fixes it up.
[PACKET]: Fix skb->cb clobbering between aux and sockaddr
Both aux data and sockaddr tries to use the same buffer which
obviously doesn't work. We just happen to have 4 bytes free in
the skb->cb if you take away the maximum length of sockaddr_ll.
That's just enough to store the one piece of info from aux data
that we can't generate at recvmsg(2) time.
This is what the following patch does.
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Cheers,
--
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index dab117e..4c7f9d7 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -60,6 +60,7 @@
#include <linux/netdevice.h>
#include <linux/if_packet.h>
#include <linux/wireless.h>
+#include <linux/kernel.h>
#include <linux/kmod.h>
#include <net/ip.h>
#include <net/protocol.h>
@@ -215,7 +216,15 @@ struct packet_sock {
#endif
};
-#define PACKET_SKB_CB(__skb) ((struct tpacket_auxdata *)((__skb)->cb))
+struct packet_skb_cb {
+ unsigned int origlen;
+ union {
+ struct sockaddr_pkt pkt;
+ struct sockaddr_ll ll;
+ } sa;
+};
+
+#define PACKET_SKB_CB(__skb) ((struct packet_skb_cb *)((__skb)->cb))
#ifdef CONFIG_PACKET_MMAP
@@ -296,7 +305,7 @@ static int packet_rcv_spkt(struct sk_buff *skb, struct net_device *dev, struct
/* drop conntrack reference */
nf_reset(skb);
- spkt = (struct sockaddr_pkt*)skb->cb;
+ spkt = &PACKET_SKB_CB(skb)->sa.pkt;
skb_push(skb, skb->data-skb->mac.raw);
@@ -471,7 +480,6 @@ 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 snaplen;
- struct tpacket_auxdata *aux;
if (skb->pkt_type == PACKET_LOOPBACK)
goto drop;
@@ -519,7 +527,10 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev, struct packet
skb = nskb;
}
- sll = (struct sockaddr_ll*)skb->cb;
+ BUILD_BUG_ON(sizeof(*PACKET_SKB_CB(skb)) + MAX_ADDR_LEN - 8 >
+ 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;
@@ -530,14 +541,7 @@ 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;
+ PACKET_SKB_CB(skb)->origlen = skb->len;
if (pskb_trim(skb, snaplen))
goto drop_n_acct;
@@ -1106,7 +1110,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
* it in now.
*/
- sll = (struct sockaddr_ll*)skb->cb;
+ sll = &PACKET_SKB_CB(skb)->sa.ll;
if (sock->type == SOCK_PACKET)
msg->msg_namelen = sizeof(struct sockaddr_pkt);
else
@@ -1131,11 +1135,21 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
sock_recv_timestamp(msg, sk, skb);
if (msg->msg_name)
- memcpy(msg->msg_name, skb->cb, msg->msg_namelen);
+ memcpy(msg->msg_name, &PACKET_SKB_CB(skb)->sa,
+ 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);
+ struct tpacket_auxdata aux;
+
+ 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_snaplen = skb->len;
+ aux.tp_mac = 0;
+ aux.tp_net = skb->nh.raw - skb->data;
+
+ put_cmsg(msg, SOL_PACKET, PACKET_AUXDATA, sizeof(aux), &aux);
}
/*
-
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