raddr

Report what an IP address literal means under each of the standards and implementations that disagree about it, and classify parsed values against the IANA special-purpose address registries.

The string "0177.0.0.1" is rejected by the RFC dotted-quad grammar, read as 127.0.0.1 by browsers and BSD inet_aton, and read as 177.0.0.1 by some inet_pton implementations, Apple’s among them. Most libraries pick one reading and discard the rest. raddr returns every reading, with the reason codes that explain each one, so code that validates, logs or compares addresses can see where the readings split. It reports facts, never an allow/deny verdict or a risk score. The full case, with the measured divergence tables, is the Why raddr article.

Installation

Install the released version from CRAN:

install.packages("raddr")

Or the development version from r-universe:

install.packages(
  "raddr",
  repos = c("https://bart-turczynski.r-universe.dev", "https://cloud.r-project.org")
)

raddr is pure R with no compiled code, so a source install needs no compiler and no system libraries. It performs no network access and depends only on vctrs and rlang.

Example

library(raddr)

addr_parse("0177.0.0.1")
#> <raddr_parse[1]>
#> [1] 127.0.0.1
#> Status: divergent 1
#>
#> [1] "0177.0.0.1"
#>   strict  <rejected: leading_zero>
#>   whatwg  127.0.0.1
#>   pton    177.0.0.1
#>   aton    127.0.0.1

# The browser reading reaches loopback; the inet_pton reading reaches a
# routable address.
addr_classify(addr_whatwg("0177.0.0.1"))
#> <raddr_class[1]>
#> [1] loopback 127.0.0.0/8
#> Registry: special-purpose 2025-10-09
addr_classify(addr_pton("0177.0.0.1"))
#> <raddr_class[1]>
#> [1] global 177.0.0.0/8
#> Registry: address space 2025-10-10

Learn more

The documentation site is https://bart-turczynski.gitlab.io/raddr/, with the articles listed under Articles:

• Introduction to raddr: the dialects, the parse record, and classification, worked through.
• Why raddr: the measured disagreement between standards and implementations, and what raddr leaves to other packages.
• Reason codes: every code the parse and classify layers emit.
• Edge cases: the inputs where readings and registries are easiest to get wrong.