| Message ID | 20200804133256.13494-1-ericonr@disroot.org |
|---|---|
| State | New |
| Series | "extend gethostid beyond a stub" |
| Headers | show |
diff --git a/src/misc/gethostid.c b/src/misc/gethostid.c index 25bb35db..2877842f 100644 --- a/src/misc/gethostid.c +++ b/src/misc/gethostid.c @@ -1,6 +1,18 @@ #include <unistd.h> +#include <stdio.h> long gethostid() { - return 0; + FILE *f; + long rv = 0; + + f = fopen("/etc/hostid", "reb"); + if (f) { + if (fread(&rv, 4, 1, f) == 0) { + rv = 0; + } + fclose(f); + } + + return rv; }
On Tue, Aug 4, 2020 at 6:33 AM Érico Rolim <ericonr@disroot.org> wrote: > > From: Érico Rolim <erico.erc@gmail.com> > > Implement part of the glibc behavior, where the 32-bit identifier stored > in /etc/hostid, if the file exists, is returned. If this file doesn't > contain at least 32 bits or can't be opened for some reason, return 0. > --- > > > The glibc implementation appears to read and write directly into an > > int32_t variable, without any endianness conversion. To be > > interoperable with /etc/hostid files created by glibc shouldn't musl > > skip the ntohl() and just return x ? > > I have changed it to directly read the file into a variable. Given that > the return type is long, should I still use int32_t inside the function? Yes. Consider what happens on a big-endian 64bit system. For reference, the glibc code is basically: long int gethostid (void) { int32_t id; int fd; /* First try to get the ID from a former invocation of sethostid. */ fd = __open_nocancel (HOSTIDFILE, O_RDONLY|O_LARGEFILE, 0); if (fd >= 0) { ssize_t n = __read_nocancel (fd, &id, sizeof (id)); __close_nocancel_nostatus (fd); if (n == sizeof (id)) return id; } ... } > src/misc/gethostid.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/src/misc/gethostid.c b/src/misc/gethostid.c > index 25bb35db..2877842f 100644 > --- a/src/misc/gethostid.c > +++ b/src/misc/gethostid.c > @@ -1,6 +1,18 @@ > #include <unistd.h> > +#include <stdio.h> > > long gethostid() > { > - return 0; > + FILE *f; > + long rv = 0; > + > + f = fopen("/etc/hostid", "reb"); > + if (f) { > + if (fread(&rv, 4, 1, f) == 0) { > + rv = 0; > + } > + fclose(f); > + } > + > + return rv; > } > -- > 2.28.0 >