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Date: Fri, 13 Mar 2020 22:46:48 +0100
From: Wolf <wolf@...fsden.cz>
To: musl@...ts.openwall.com
Subject: Proposal to match behaviour of gethostbyname to glibc
Hello,
today I've noticed difference in behavior of gethostbyname in musl and
in glibc. Given /etc/hosts
127.0.0.1 foo.bar foo
127.0.0.1 bar.foo foo
and simple test program
#include <netdb.h>
#include <stdio.h>
int main(int argc, char **argv) {
struct hostent *he = gethostbyname(argv[1]);
printf("Hostname: %s\n", he->h_name);
}
, I've run it both under musl (alpine) and glibc (archlinux).
musl:
/test # ./test foo
Hostname: bar.foo
glibc:
[root@foo test]# ./test foo
Hostname: foo.bar
I don't think there is an actual reason to iterate through all of the
/etc/hosts and first match can be returned instead. Following patch
should in my opinion fix this.
diff --git a/src/network/lookup_name.c b/src/network/lookup_name.c
index c93263a9..da8db9d4 100644
--- a/src/network/lookup_name.c
+++ b/src/network/lookup_name.c
@@ -87,7 +87,10 @@ static int name_from_hosts(struct address buf[static MAXADDRS], char canon[stati
for (; *p && isspace(*p); p++);
for (z=p; *z && !isspace(*z); z++);
*z = 0;
- if (is_valid_hostname(p)) memcpy(canon, p, z-p+1);
+ if (is_valid_hostname(p)) {
+ memcpy(canon, p, z-p+1);
+ break;
+ }
}
__fclose_ca(f);
return cnt ? cnt : badfam;
While this is admittedly edge case that most users will not run into, I
still think it would be nice to behave the same way as glibc does on
this one. And as a bonus, it will be *tiny* bit faster, since there
would not be any need to iterate rest of the /etc/hosts file.
Thank you for considering this,
W.
--
There are only two hard things in Computer Science:
cache invalidation, naming things and off-by-one errors.
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