* icmp_hdr is wrong on CentOS 6 kernels (2.6.32-754.12.1)
@ 2019-09-18 2:53 Olivia Nelson
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From: Olivia Nelson @ 2019-09-18 2:53 UTC (permalink / raw)
To: netfilter-devel
I have a simple netfilter module to test icmp_hdr function:
unsigned int hook_func(
unsigned int hooknum,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
const struct iphdr *ip_header = ip_hdr(skb);
if (ip_header && ip_header->protocol == IPPROTO_ICMP)
{
const struct icmphdr *icmp_header = icmp_hdr(skb);
printk(KERN_INFO "ICMP type %d", icmp_header->type);
}
return NF_ACCEPT;
}
Then I start to PING the HOST.
On CentOS 6 (2.6.32-754.12.1.el6.x86_64), he printed ICMP type is
always 69 (INVALID).
On CentOS 7 (3.10) the result is ICMP_ECHO (8), which is correct.
Was it a bug?
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