Map a host IP and a subnet length into a subnet range

[synikitin]

Hello,

I ran into an issue of mapping host ips and subnet lengths collected from flow data into subnet ranges, and did not find a way to make it with the current version of iptools. Here is a working function I wrote to solve the problem:

library(magrittr)

host_ip <- c("1.2.3.4", "4.3.2.1")
subnet_len <- c(24L, 25L)

ip_to_subnet <- function(host_ip, subnet_len) {
  
  # binary representation of host ips
  ip <- iptools::ip_to_binary_string(host_ip) %>% 
    stringr::str_split("", simplify = TRUE) %>% 
    `mode<-`("double")
  
  # binary representation of subnet masks
  default_mask <- stringr::str_c(rep("0", 32L), collapse = "")
  mask <- stringr::`str_sub<-`(
    default_mask,
    start = 1, end = subnet_len,
    value = stringr::str_dup("1", subnet_len)
    ) %>% 
    stringr::str_split("", simplify = TRUE) %>% 
    `mode<-`("double")
  
  # numeric representation of subnet ips
  subnet_ip <- iptools::numeric_to_ip(
    (ip * mask) %*% 2 ^ (31:0)
  )
  
  # octet representation of subnet ranges
  subnet_range <- stringr::str_c(subnet_ip, subnet_len, sep = "/")
  subnet_range
}


ip_to_subnet(host_ip, subnet_len)

Maybe a variant of this can make into the package.

[hrbrmstr]

Many thanks for using the package and submitting this!

I ended up using the underlying Boost AsioHeaders network_v4 class functions for this and added a convenience wrapper for it (https://github.com/hrbrmstr/iptools/blob/master/R/ip-to-subnet.R#L1-L41)

host_ip <- c("1.2.3.4", "4.3.2.1")
subnet_len <- c(24L, 25L)
ip_to_subnet(host_ip, subnet_len)
## [1] "1.2.3.0/24" "4.3.2.0/25"

ip_to_subnet(c("1.2.3.4/24", "4.3.2.1/25"))
## [1] "1.2.3.0/24" "4.3.2.0/25"

Let me know if it doesn't handle any inputs you toss at it (I've only done light testing).

It should be on the main branch now.