No reference implementation for getifaddrs available for this platform

[voltagex]

I'm building against an ancient uclibc (not my choice) and I can't build libimobiledevice-glue

make  all-recursive
make[1]: Entering directory '/src/libimobiledevice-glue'
Making all in src
make[2]: Entering directory '/src/libimobiledevice-glue/src'
  CC     socket.lo
socket.c:698:2: error: #error No reference implementation for getifaddrs available for this platform.

All I'm after in the end is USB tethering, is it possible to #ifdef out all the wifi based stuff as well?

Otherwise, I note that you've got a portable-ish getifaddrs for Windows in socket.c, could this be made to work for uclibc as well?

[voltagex]

Strangely, while stubbing it, I see /src/am-toolchains/brcm-arm-sdk/hndtools-arm-linux-2.6.36-uclibc-4.5.3/bin/../arm-brcm-linux-uclibcgnueabi/sysroot/usr/include/ifaddrs.h:59:12: note: previous declaration of 'getifaddrs' was here, so maybe the #ifdefs are just incorrect?

[nikias]

Hi, something in configure doesn't seem to work out. A simple workaround would be to set the environment variable ac_cv_func_getifaddrs=yes before running configure. But I'd prefer to fix this to detect it properly. Can you apply this patch and re-run ./autogen.sh?

diff --git a/configure.ac b/configure.ac
index bfc443e..799a2ab 100644
--- a/configure.ac
+++ b/configure.ac
@@ -44,7 +44,11 @@ AC_TYPE_UINT32_T
 AC_TYPE_UINT8_T

 # Checks for library functions.
-AC_CHECK_FUNCS([asprintf strcasecmp strdup strerror strndup stpcpy vasprintf getifaddrs])
+AC_CHECK_FUNCS([asprintf strcasecmp strdup strerror strndup stpcpy vasprintf])
+
+# Check for additional functions
+AC_CHECK_HEADERS(ifaddrs.h)
+AC_CHECK_FUNCS(getifaddrs)

 # Check for operating system
 AC_MSG_CHECKING([for platform-specific build settings])```

[nikias]

Hmm... guess that doesn't really make a difference...

[voltagex]

Hmm... guess that doesn't really make a difference...

I don't have direct access to this device at the moment but my workaround was this

https://git.sr.ht/~voltagex/rt68u-itethering/tree/main/item/getifaddrs-stub.patch

[nikias]

I see... Next time you do, could you check config.log, search for getifaddrs and paste the lines around it? That would be really helpful.
What the check basically does is something like:

#ifdef __cplusplus
extern "C"
#endif
char getifaddrs();

int
main ()
{
  return getifaddrs();

  return 0;
}

And then it tries to link that trying to see if that symbol exists. Something like
/your/cool/compiler/gcc -o conftest conftest.c

Thanks for trying to figure this out.

[voltagex]

config.log, search for getifaddrs

With or without your patch?

[nikias]

Without. The patch is not really changing anything :)

[voltagex]

Apologies for the delay in getting back to you, @nikias.
I have re-run the commands and attached logs here.

config.log.txt
make.txt

[nikias]

No problem at all. So it looks like it expects the symbol to be in some library after all:

configure:8736: checking for getifaddrs
configure:8736: arm-brcm-linux-uclibcgnueabi-gcc -std=gnu99 -o conftest -I/opt/brcm-arm/include -L/opt/brcm-arm/lib  -lplist-2.0 -lpthread -lrt conftest.c -lplist-2.0 -lpthread -lrt >&5
/tmp/ccOprCHS.o: In function `main':
conftest.c:(.text+0x8): undefined reference to `getifaddrs'

Any idea what library that could be? Maybe /opt/brcm-arm/lib holds it. Try this command (notice the + at the end!)

find /opt/brcm-arm/lib -name "*.so" -exec sh -c 'for i; do VAL=`nm $i |grep "T _getifaddrs"`; if test -n "$VAL"; then echo $i; echo $VAL; fi; done' sh {} +

[voltagex]

Yeah, this is in Broadcom's proprietary (?) toolchain (?), in libshared.so - but when I looked again I actually did find it in AsusWRT Merlin

nm: /opt/brcm-arm/lib/ld-uClibc-0.9.32.1.so: no symbols
nm: /opt/brcm-arm/lib/libc.so: no symbols
nm: /opt/brcm-arm/lib/libcrypt-0.9.32.1.so: no symbols
nm: /opt/brcm-arm/lib/libdl-0.9.32.1.so: no symbols
nm: /opt/brcm-arm/lib/libgcc_s.so: file format not recognized
nm: /opt/brcm-arm/lib/libm-0.9.32.1.so: no symbols
nm: /opt/brcm-arm/lib/libnsl-0.9.32.1.so: no symbols
nm: /opt/brcm-arm/lib/libresolv-0.9.32.1.so: no symbols
nm: /opt/brcm-arm/lib/librt-0.9.32.1.so: no symbols
nm: /opt/brcm-arm/lib/libthread_db-0.9.32.1.so: no symbols
nm: /opt/brcm-arm/lib/libuClibc-0.9.32.1.so: no symbols
nm: /opt/brcm-arm/lib/libutil-0.9.32.1.so: no symbols

https://github.com/RMerl/asuswrt-merlin.ng/blob/8a77382a6ea8c86e102fbd0d8b2cb0f58c7b81c6/release/src/router/shared/ifaddrs.c

I ended up writing a shim to make the thing build, and then it looks like the symbol/.so is available on the device itself - unpacking the trx file (using 7zip) from wget https://sourceforge.net/projects/asuswrt-merlin/files/RT-AC68U/Release/RT-AC68U_386.4_0.zip, I can see the symbols.

strings ./usr/lib/libshared.so | grep ifaddrs
getifaddrs
freeifaddrs
getifaddrs failed: %s
getifaddrs netmask error: %x

Sorry, this is probably really offtopic for your project - it's not a libimobiledevice issue, however, setting the autoconf variable then leads to

/opt/brcm-arm/lib/libimobiledevice-glue-1.0.so: undefined reference to `freeifaddrs'
/opt/brcm-arm/lib/libimobiledevice-glue-1.0.so: undefined reference to `getifaddrs'

as soon as something tries to link with libimobiledevice-glue.

[nikias]

I agree this is really specific, but nonetheless it should be possible to get this to link somehow.
So would it work if you link with -lshared ?

[voltagex]

-lshared fails unless I use the shim from my repo. If I get some time I'll try to get in contact with the Merlin devs and see if they can make a change so that the libshared library is available

[nikias]

OK, thanks. Your patch only adds the ifaddr.h include, is that defining the functions?

[voltagex]

Yes, only the functions, and just barely.

[JonasVautherin]

I have the exact same issue when cross-compiling for Android (using dockcross). @voltagex's patch fixes the build, but I understand it is not ideal:

diff --git a/src/socket.c b/src/socket.c
index ad6135f..61da815 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -695,7 +695,8 @@ static int getifaddrs(struct ifaddrs** ifap)
 	return 0;
 }
 #else
-#error No reference implementation for getifaddrs available for this platform.
+#warning No reference implementation for getifaddrs available for this platform.
+#include "ifaddrs.h"
 #endif
 #endif

For me, config.log says:

configure:13345: checking for getifaddrs
configure:13345: /usr/aarch64-linux-android/bin/clang -o conftest -g -O2   conftest.c  >&5
ld: error: undefined symbol: getifaddrs
>>> referenced by conftest.c:60
>>>               /tmp/conftest-deaa86.o:(main)
clang140: error: linker command failed with exit code 1 (use -v to see invocation)

Though I have ifaddrs.h in /usr/include and in /usr/aarch64-linux-android/sysroot/usr/include 🤔.

@nikias: any suggestion what else I should check?