sockaddr_in Returns Port 0 When Passed Regexp Capture in Recent Perl Versions

[akiya-i]

generated with the help of perlbug 1.43 running under perl 5.38.2.

---

Description

If a regular expression capture is passed as the port number to pack_sockaddr_in(),
the argument may not be correctly interpreted as a number, resulting in a sockaddr_in structure with port=0.

This issue arises in code from the IO::Socket::Multicast module.

I encountered this problem while using a multicast UDP send script with the IO::Socket::Multicast module.

You can reproduce the issue using the mcast_dest_test2 script:

• test_dest("{IP}:{port}") creates a sockaddr_in structure with port=0.
• test_dest2("{IP}:{port}") works correctly.
• If test_dest("{IP}:{port}") is called again afterwards, it also works correctly.

This problem does NOT occur with Perl 5.24.1.
However, starting with Perl 5.32.1 and continuing through 5.40.2, the issue does occur.

---- BEGIN mcast_dest_test2 ----

#!/usr/bin/perl

use strict;
use Socket;

my $mcasaddr="239.32.13.1:51301";

my $IP = '\d+\.\d+\.\d+\.\d+';

sub test_dest
{
	my $dest;
	if ($dest = shift) {							 
		$dest = sockaddr_in($2,inet_aton($1)) if $dest =~ /^($IP):(\d+)$/;	  
		print "invalid destination address" unless length($dest) == 16;   
	}

	my ($port,$ip) = sockaddr_in($dest);
	print "sockaddr = ($port, ",inet_ntoa($ip),")\n";
}		  
sub test_dest2
{
	my $dest;
	if ($dest = shift) {							 
		$dest = sockaddr_in(int($2),inet_aton($1)) if $dest =~ /^($IP):(\d+)$/;        
		print "invalid destination address" unless length($dest) == 16;   
	}

	my ($port,$ip) = sockaddr_in($dest);
	print "sockaddr2 = ($port, ",inet_ntoa($ip),")\n";
}		  

test_dest($mcasaddr);

test_dest2($mcasaddr);

test_dest($mcasaddr);

---- END mcast_dest_test2 ----

Steps to Reproduce

perl mcast_dest_test2

Expected behavior

perl 5.24.1 returns what I expect.

sockaddr = (51301, 239.32.13.1)
sockaddr2 = (51301, 239.32.13.1)
sockaddr = (51301, 239.32.13.1)

but perl 5.38.2 returns wrong.

sockaddr = (0, 239.32.13.1)
sockaddr2 = (51301, 239.32.13.1)
sockaddr = (51301, 239.32.13.1)

---

Flags

• category=core
• severity=low

---

Perl configuration

Site configuration information for perl 5.38.2:

Configured by Ubuntu at Tue Apr  8 12:47:54 UTC 2025.

Summary of my perl5 (revision 5 version 38 subversion 2) configuration:
   
  Platform:
    osname=linux
    osvers=6.1.0
    archname=x86_64-linux-gnu-thread-multi
    uname='linux localhost 6.1.0 #1 smp debian 6.1.0 x86_64 gnulinux '
    config_args='-Dmksymlinks -Dusethreads -Duselargefiles -Dcc=x86_64-linux-gnu-gcc -Dcpp=x86_64-linux-gnu-cpp -Dld=x86_64-linux-gnu-gcc -Dccflags=-DDEBIAN -Wdate-time -D_FORTIFY_SOURCE=3 -g -O2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -ffile-prefix-map=/dummy/build/dir=. -flto=auto -ffat-lto-objects -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -fdebug-prefix-map=/dummy/build/dir=/usr/src/perl-5.38.2-3.2ubuntu0.1 -Dldflags= -Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -Wl,-z,relro -Dlddlflags=-shared -Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -Wl,-z,relro -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.38 -Darchlib=/usr/lib/x86_64-linux-gnu/perl/5.38 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/x86_64-linux-gnu/perl5/5.38
-Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.38.2 -Dsitearch=/usr/local/lib/x86_64-linux-gnu/perl/5.38.2 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Duse64bitint -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -Ui_libutil -Ui_xlocale -Uversiononly -Ud_strlcpy -Ud_strlcat -DDEBUGGING=-g -Doptimize=-O2 -dEs -Duseshrplib -Dlibperl=libperl.so.5.38.2'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=define
    usemultiplicity=define
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
  Compiler:
    cc='x86_64-linux-gnu-gcc'
    ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
    optimize='-O2 -g'
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv -fno-strict-aliasing -pipe -I/usr/local/include'
    ccversion=''
    gccversion='13.3.0'
    gccosandvers=''
    intsize=4
    longsize=8
    ptrsize=8
    doublesize=8
    byteorder=12345678
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=16
    longdblkind=3
    ivtype='long'
    ivsize=8
    nvtype='double'
    nvsize=8
    Off_t='off_t'
    lseeksize=8
    alignbytes=8
    prototype=define
  Linker and Libraries:
    ld='x86_64-linux-gnu-gcc'
    ldflags =' -fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=/lib/x86_64-linux-gnu/libc.so.6
    so=so
    useshrplib=true
    libperl=libperl.so.5.38
    gnulibc_version='2.39'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -L/usr/local/lib -fstack-protector-strong'

Locally applied patches:
    DEBPKG:debian/cpan_definstalldirs - Provide a sensible INSTALLDIRS default for modules installed from CPAN.
    DEBPKG:debian/db_file_ver - https://bugs.debian.org/340047 Remove overly restrictive DB_File version check.
    DEBPKG:debian/doc_info - Replace generic man(1) instructions with Debian-specific information.
    DEBPKG:debian/enc2xs_inc - https://bugs.debian.org/290336 Tweak enc2xs to follow symlinks and ignore missing @INC directories.
    DEBPKG:debian/errno_ver - https://bugs.debian.org/343351 Remove Errno version check due to upgrade problems with long-running processes.
    DEBPKG:debian/libperl_embed_doc - https://bugs.debian.org/186778 Note that libperl-dev package is required for embedded linking
    DEBPKG:fixes/respect_umask - Respect umask during installation
    DEBPKG:debian/writable_site_dirs - Set umask approproately for site install directories
    DEBPKG:debian/extutils_set_libperl_path - EU:MM: set location of libperl.a under /usr/lib
    DEBPKG:debian/no_packlist_perllocal - Don't install .packlist or perllocal.pod for perl or vendor
    DEBPKG:debian/fakeroot - Postpone LD_LIBRARY_PATH evaluation to the binary targets.
    DEBPKG:debian/instmodsh_doc - Debian policy doesn't install .packlist files for core or vendor.
    DEBPKG:debian/ld_run_path - Remove standard libs from LD_RUN_PATH as per Debian policy.
    DEBPKG:debian/libnet_config_path - Set location of libnet.cfg to /etc/perl/Net as /usr may not be writable.
    DEBPKG:debian/perlivp - https://bugs.debian.org/510895 Make perlivp skip include directories in /usr/local
    DEBPKG:debian/squelch-locale-warnings - https://bugs.debian.org/508764 Squelch locale warnings in Debian package maintainer scripts
    DEBPKG:debian/patchlevel - https://bugs.debian.org/567489 List packaged patches for 5.38.2-3.2ubuntu0.1 in patchlevel.h
    DEBPKG:fixes/document_makemaker_ccflags - https://bugs.debian.org/628522 [rt.cpan.org #68613] Document that CCFLAGS should include $Config{ccflags}
    DEBPKG:debian/find_html2text - https://bugs.debian.org/640479 Configure CPAN::Distribution with correct name of html2text
    DEBPKG:debian/perl5db-x-terminal-emulator.patch - https://bugs.debian.org/668490 Invoke x-terminal-emulator rather than xterm in perl5db.pl
    DEBPKG:debian/cpan-missing-site-dirs - https://bugs.debian.org/688842 Fix CPAN::FirstTime defaults with nonexisting site dirs if a parent is writable
    DEBPKG:debian/makemaker-pasthru - https://bugs.debian.org/758471 Pass LD settings through to subdirectories
    DEBPKG:debian/makemaker-manext - https://bugs.debian.org/247370 Make EU::MakeMaker honour MANnEXT settings in generated manpage headers
    DEBPKG:debian/kfreebsd-softupdates - https://bugs.debian.org/796798 Work around Debian Bug#796798
    DEBPKG:debian/hurd-softupdates - https://bugs.debian.org/822735 Fix t/op/stat.t failures on hurd
    DEBPKG:fixes/math_complex_doc_great_circle - https://bugs.debian.org/697567 [rt.cpan.org #114104] Math::Trig: clarify definition of great_circle_midpoint
    DEBPKG:fixes/math_complex_doc_angle_units - https://bugs.debian.org/731505 [rt.cpan.org #114106] Math::Trig: document angle units
    DEBPKG:fixes/cpan_web_link - https://bugs.debian.org/367291 CPAN: Add link to main CPAN web site
    DEBPKG:debian/installman-utf8 - https://bugs.debian.org/840211 Generate man pages with UTF-8 characters
    DEBPKG:debian/perldoc-pager - https://bugs.debian.org/870340 [rt.cpan.org #120229] Fix perldoc terminal escapes when sensible-pager is less
    DEBPKG:debian/prune_libs - https://bugs.debian.org/128355 Prune the list of libraries wanted to what we actually need.
    DEBPKG:debian/mod_paths - Tweak @INC ordering for Debian
    DEBPKG:debian/deprecate-with-apt - https://bugs.debian.org/747628 Point users to Debian packages of deprecated core modules
    DEBPKG:debian/disable-stack-check - https://bugs.debian.org/902779 [GH #16607] Disable debugperl stack extension checks for binary compatibility with perl
    DEBPKG:debian/perlbug-editor - https://bugs.debian.org/922609 Use "editor" as the default perlbug editor, as per Debian policy
    DEBPKG:debian/eu-mm-perl-base - https://bugs.debian.org/962138 Suppress an ExtUtils::MakeMaker warning about our non-default @INC
    DEBPKG:fixes/io_socket_ip_ipv6 - Disable getaddrinfo(3) AI_ADDRCONFIG for localhost and IPv4 numeric addresses
    DEBPKG:debian/usrmerge-lib64 - https://bugs.debian.org/914128 Configure / libpth.U: Do not adjust glibpth when /usr/lib64 is present.
    DEBPKG:debian/usrmerge-realpath - https://bugs.debian.org/914128 Configure / libpth.U: use realpath --no-symlinks on Debian
    DEBPKG:fixes/x32-io-msg-skip - https://bugs.debian.org/922609 Skip io/msg.t on x32 due to broken System V message queues
    DEBPKG:debian/configure-regen - https://bugs.debian.org/762638 Regenerate Configure et al. after probe unit changes
    DEBPKG:fixes/bignum-recursion - https://bugs.debian.org/1012704 [rt.cpan.org #146411] Fix CPAN RT #146411
    DEBPKG:fixes/math-bigfloat-subclass - https://bugs.debian.org/1043234 Fix Math::BigFloat subclass numeric comparison
    DEBPKG:fixes/unbreak-locale-initialization - [GH #21366] https://bugs.debian.org/1060679 Revert "locale.c: Do uselocale() earlier in init process"
    DEBPKG:CVE-2024-56406.patch -

---
@INC for perl 5.38.2:
    /etc/perl
    /usr/local/lib/x86_64-linux-gnu/perl/5.38.2
    /usr/local/share/perl/5.38.2
    /usr/lib/x86_64-linux-gnu/perl5/5.38
    /usr/share/perl5
    /usr/lib/x86_64-linux-gnu/perl-base
    /usr/lib/x86_64-linux-gnu/perl/5.38
    /usr/share/perl/5.38
    /usr/local/lib/site_perl

---
Environment for perl 5.38.2:
    HOME=/home/aya
    LANG=ja_JP.UTF-8
    LANGUAGE=ja:en_US:en
    LC_ADDRESS=en_US.UTF-8
    LC_COLLATE=C
    LC_IDENTIFICATION=en_US.UTF-8
    LC_MEASUREMENT=en_US.UTF-8
    LC_MESSAGES=C
    LC_MONETARY=en_US.UTF-8
    LC_NAME=en_US.UTF-8
    LC_NUMERIC=en_US.UTF-8
    LC_PAPER=en_US.UTF-8
    LC_TELEPHONE=en_US.UTF-8
    LC_TIME=C
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/aya/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/snap/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

[iabyn]

On Mon, Jun 02, 2025 at 09:46:11PM -0700, Akiya ISHIDA wrote: If a regular expression capture is passed as the port number to pack_sockaddr_in(), the argument may not be correctly interpreted as a number, resulting in a sockaddr_in structure with port=0.

I've reduced the issue to this code: ``` use Socket; "2057" =~ /^(\d+)$/ or die; # 2057 == 0x0809 my $dest = sockaddr_in($1, "\x11\x22\x33\x44"); printf "%vx\n", $dest; ``` which gives: $ perl5260 /tmp/foo 2.0.8.9.11.22.33.44.0.0.0.0.0.0.0.0 $ perl5280 /tmp/foo 2.0.0.0.11.22.33.44.0.0.0.0.0.0.0.0 It's an issue in the Socket distribution, which is maintained separately. I've raised this ticket for it: https://rt.cpan.org/Ticket/Display.html?id=166524 A workaround for the issue in the meantime is to stringify the value; so in the example above, do my $dest = sockaddr_in("$1", "\x11\x22\x33\x44");

…

-- Any [programming] language that doesn't occasionally surprise the novice will pay for it by continually surprising the expert. -- Larry Wall