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drivers/net/wan/hdlc_fr: Correctly handle special skb->protocol values 

The fr_hard_header function is used to prepend the header to skbs before
transmission. It is used in 3 situations:
1) When a control packet is generated internally in this driver;
2) When a user sends an skb on an Ethernet-emulating PVC device;
3) When a user sends an skb on a normal PVC device.

These 3 situations need to be handled differently by fr_hard_header.
Different headers should be prepended to the skb in different situations.

Currently fr_hard_header distinguishes these 3 situations using
skb->protocol. For situation 1 and 2, a special skb->protocol value
will be assigned before calling fr_hard_header, so that it can recognize
these 2 situations. All skb->protocol values other than these special ones
are treated by fr_hard_header as situation 3.

However, it is possible that in situation 3, the user sends an skb with
one of the special skb->protocol values. In this case, fr_hard_header
would incorrectly treat it as situation 1 or 2.

This patch tries to solve this issue by using skb->dev instead of
skb->protocol to distinguish between these 3 situations. For situation
1, skb->dev would be NULL; for situation 2, skb->dev->type would be
ARPHRD_ETHER; and for situation 3, skb->dev->type would be ARPHRD_DLCI.

This way fr_hard_header would be able to distinguish these 3 situations
correctly regardless what skb->protocol value the user tries to use in
situation 3.

Cc: Krzysztof Halasa <khc@pm.waw.pl>
Signed-off-by: Xie He <xie.he.0141@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xie He 2020-09-28 05:56:43 -07:00 committed by David S. Miller
parent 23a1f682a9
commit 8306266c1d
1 changed files with 47 additions and 43 deletions
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90
drivers/net/wan/hdlc_fr.c
View File

@ -273,63 +273,69 @@ static inline struct net_device **get_dev_p(struct pvc_device *pvc,
static int fr_hard_header(struct sk_buff **skb_p, u16 dlci)
{
u16 head_len;
struct sk_buff *skb = *skb_p;
switch (skb->protocol) {
case cpu_to_be16(NLPID_CCITT_ANSI_LMI):
head_len = 4;
skb_push(skb, head_len);
skb->data[3] = NLPID_CCITT_ANSI_LMI;
break;
if (!skb->dev) { /* Control packets */
switch (dlci) {
case LMI_CCITT_ANSI_DLCI:
skb_push(skb, 4);
skb->data[3] = NLPID_CCITT_ANSI_LMI;
break;
case cpu_to_be16(NLPID_CISCO_LMI):
head_len = 4;
skb_push(skb, head_len);
skb->data[3] = NLPID_CISCO_LMI;
break;
case LMI_CISCO_DLCI:
skb_push(skb, 4);
skb->data[3] = NLPID_CISCO_LMI;
break;
case cpu_to_be16(ETH_P_IP):
head_len = 4;
skb_push(skb, head_len);
skb->data[3] = NLPID_IP;
break;
default:
return -EINVAL;
}
case cpu_to_be16(ETH_P_IPV6):
head_len = 4;
skb_push(skb, head_len);
skb->data[3] = NLPID_IPV6;
break;
} else if (skb->dev->type == ARPHRD_DLCI) {
switch (skb->protocol) {
case htons(ETH_P_IP):
skb_push(skb, 4);
skb->data[3] = NLPID_IP;
break;
case cpu_to_be16(ETH_P_802_3):
head_len = 10;
if (skb_headroom(skb) < head_len) {
struct sk_buff *skb2 = skb_realloc_headroom(skb,
head_len);
case htons(ETH_P_IPV6):
skb_push(skb, 4);
skb->data[3] = NLPID_IPV6;
break;
default:
skb_push(skb, 10);
skb->data[3] = FR_PAD;
skb->data[4] = NLPID_SNAP;
/* OUI 00-00-00 indicates an Ethertype follows */
skb->data[5] = 0x00;
skb->data[6] = 0x00;
skb->data[7] = 0x00;
/* This should be an Ethertype: */
*(__be16 *)(skb->data + 8) = skb->protocol;
}
} else if (skb->dev->type == ARPHRD_ETHER) {
if (skb_headroom(skb) < 10) {
struct sk_buff *skb2 = skb_realloc_headroom(skb, 10);
if (!skb2)
return -ENOBUFS;
dev_kfree_skb(skb);
skb = *skb_p = skb2;
}
skb_push(skb, head_len);
skb_push(skb, 10);
skb->data[3] = FR_PAD;
skb->data[4] = NLPID_SNAP;
skb->data[5] = FR_PAD;
/* OUI 00-80-C2 stands for the 802.1 organization */
skb->data[5] = 0x00;
skb->data[6] = 0x80;
skb->data[7] = 0xC2;
/* PID 00-07 stands for Ethernet frames without FCS */
skb->data[8] = 0x00;
skb->data[9] = 0x07; /* bridged Ethernet frame w/out FCS */
break;
skb->data[9] = 0x07;
default:
head_len = 10;
skb_push(skb, head_len);
skb->data[3] = FR_PAD;
skb->data[4] = NLPID_SNAP;
skb->data[5] = FR_PAD;
skb->data[6] = FR_PAD;
skb->data[7] = FR_PAD;
*(__be16*)(skb->data + 8) = skb->protocol;
} else {
return -EINVAL;
}
dlci_to_q922(skb->data, dlci);
@ -425,8 +431,8 @@ static netdev_tx_t pvc_xmit(struct sk_buff *skb, struct net_device *dev)
skb_put(skb, pad);
memset(skb->data + len, 0, pad);
}
skb->protocol = cpu_to_be16(ETH_P_802_3);
}
skb->dev = dev;
if (!fr_hard_header(&skb, pvc->dlci)) {
dev->stats.tx_bytes += skb->len;
dev->stats.tx_packets++;
@ -494,10 +500,8 @@ static void fr_lmi_send(struct net_device *dev, int fullrep)
memset(skb->data, 0, len);
skb_reserve(skb, 4);
if (lmi == LMI_CISCO) {
skb->protocol = cpu_to_be16(NLPID_CISCO_LMI);
fr_hard_header(&skb, LMI_CISCO_DLCI);
} else {
skb->protocol = cpu_to_be16(NLPID_CCITT_ANSI_LMI);
fr_hard_header(&skb, LMI_CCITT_ANSI_DLCI);
}
data = skb_tail_pointer(skb);