IP-address from sk_buff
Solution 1
There are two macros defined in include/linux/kernel.h
NIPQUAD for ipv4 addresses and NIP6 for ipv6 addresses.
#define NIPQUAD(addr) \
((unsigned char *)&addr)[0], \
((unsigned char *)&addr)[1], \
((unsigned char *)&addr)[2], \
((unsigned char *)&addr)[3]
#define NIP6(addr) \
ntohs((addr).s6_addr16[0]), \
ntohs((addr).s6_addr16[1]), \
ntohs((addr).s6_addr16[2]), \
ntohs((addr).s6_addr16[3]), \
ntohs((addr).s6_addr16[4]), \
ntohs((addr).s6_addr16[5]), \
ntohs((addr).s6_addr16[6]), \
ntohs((addr).s6_addr16[7])
There are ample examples in the kernel sources that make use of these to print ip addresses in human-readable format. For instance:
printk(KERN_DEBUG "Received packet from source address: %d.%d.%d.%d!\n",NIPQUAD(iph->saddr));
Hope this helps.
Solution 2
You should use the %pI4 extended format specifiers provided by printk():
printk(KERN_DEBUG "IP addres = %pI4\n", &local_ip);
Solution 3
printk can handle this directly:
IPv4 addresses:
%pI4 1.2.3.4
%pi4 001.002.003.004
%p[Ii]4[hnbl]
For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
specifiers result in a printed address with ('i4') or without ('I4')
leading zeros.
The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
host, network, big or little endian order addresses respectively. Where
no specifier is provided the default network/big endian order is used.
Passed by reference.
IPv6 addresses:
%pI6 0001:0002:0003:0004:0005:0006:0007:0008
%pi6 00010002000300040005000600070008
%pI6c 1:2:3:4:5:6:7:8
For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
specifiers result in a printed address with ('I6') or without ('i6')
colon-separators. Leading zeros are always used.
The additional 'c' specifier can be used with the 'I' specifier to
print a compressed IPv6 address as described by
http://tools.ietf.org/html/rfc5952
Passed by reference.
Reference: https://www.kernel.org/doc/Documentation/printk-formats.txt
Solution 4
Simple. The IP address in "x.x.x.x" format is called dotted-quad for a reason. Each number represents a byte, for a total of 4 bytes in your address.
So, with the 4 byte address, you would simply print the decimal value of each byte.
Quick and dirty example (replace printf with your output function of choice):
unsigned char *addr = (unsigned char*)sk_buff->addr;
printf("%d.%d.%d.%d", addr[0], addr[1], addr[2], addr[3]);
Rohit
Updated on June 04, 2022Comments
-
Rohit almost 2 years
I am writing a kernel module which registers a netfilter hook. I am trying to get the ip address of the caller by using the
sk_buff->saddr
member. Is there a way I can get the IP in human readable i.e. x.x.x.x format?I found the function
inet_ntop()
but it doesn't seem to be available in kernel headers. How do I convert \xC0\xA8\x00\x01 to 192.168.0.1 ? -
Tim Post about 15 yearsI'm almost positive that a macro exists which does just that, I just can't find it ATM.
-
pratikm about 12 yearsI ran across this now. For the benefit of others who may stumble across this,
NIPQUAD
has been ellimated after 2.6.38. Use%pI4
instead -
BonBon almost 7 yearsCame across this later. There is now
in4_pton()
in /net/core/utils.c -
Stefan about 6 years@BonBon:
in4_pton()
does the reverse.