编译hostapd时 出现错误：/usr/bin/ld: cannot find -lnl

book@ubuntu:/work/project/wifi/04.hostapd/hostapd-2.0/hostapd$ make

/usr/bin/ld: cannot find -lnl

collect2: ld returned 1 exit status

make: *** [hostapd] Error 1

问题原因是，没有找到 nl 库 ！

然后我搜索 这个 nl 库是在哪儿被使用的：

book@ubuntu:/work/project/wifi/04.hostapd/hostapd-2.0$ grep "\-lnl" * -nR

src/drivers/drivers.mak:31: DRV_LIBS += -lnl-3

src/drivers/drivers.mak:32: DRV_LIBS += -lnl-genl-3

src/drivers/drivers.mak:36: DRV_LIBS += -lnl-tiny

src/drivers/drivers.mak:38: DRV_LIBS += -lnl

src/drivers/drivers.mak:42: DRV_LIBS += -lnl-genl

src/drivers/drivers.mak:148: DRV_LIBS += -lnl-3

src/drivers/drivers.mak:149: DRV_LIBS += -lnl-genl-3

src/drivers/drivers.mak:150: DRV_LIBS += -lnl-route-3

src/drivers/drivers.mak:154: DRV_LIBS += -lnl-tiny

src/drivers/drivers.mak:156: DRV_LIBS += -lnl

src/drivers/drivers.mak:160: DRV_LIBS += -lnl-genl

src/drivers/drivers.mak:161: DRV_LIBS += -lnl-route

src/drivers/drivers.mk:31: DRV_LIBS += -lnl-3

src/drivers/drivers.mk:32: DRV_LIBS += -lnl-genl-3

src/drivers/drivers.mk:36: DRV_LIBS += -lnl-tiny

src/drivers/drivers.mk:38: DRV_LIBS += -lnl

src/drivers/drivers.mk:42: DRV_LIBS += -lnl-genl

src/drivers/drivers.mk:152: DRV_LIBS += -lnl-3

src/drivers/drivers.mk:153: DRV_LIBS += -lnl-genl-3

src/drivers/drivers.mk:154: DRV_LIBS += -lnl-route-3

src/drivers/drivers.mk:158: DRV_LIBS += -lnl-tiny

src/drivers/drivers.mk:160: DRV_LIBS += -lnl

src/drivers/drivers.mk:164: DRV_LIBS += -lnl-genl

src/drivers/drivers.mk:165: DRV_LIBS += -lnl-route

然后，我们查看交叉编译库里 有没有 nl 的库

/usr/local/arm/4.3.2/arm-none-linux-gnueabi/libc/armv4t/lib

然后，发现里面有这个库。

book@ubuntu:/work/project/wifi/04.hostapd/hostapd-2.0$ ls /usr/local/arm/4.3.2/arm-none-linux-gnueabi/libc/armv4t/libengines libnl libnsl.so.1jconfig.hlibnl-3.a libnss_compat-2.8.sojerror.hlibnl-3.la libnss_compat.so.2jmorecfg.h libnl-3.so libnss_dns-2.8.sojpeglib.hlibnl-3.so.200 libnss_dns.so.2ld-2.8.solibnl-3.so.200.18.0 libnss_files-2.8.sold-linux.so.3 libnl-cli-3.a libnss_files.so.2libanl-2.8.so libnl-cli-3.la libnss_hesiod-2.8.solibanl.so.1 libnl-cli-3.so libnss_hesiod.so.2libBrokenLocale-2.8.so libnl-cli-3.so.200 libnss_nis-2.8.solibBrokenLocale.so.1 libnl-cli-3.so.200.18.0 libnss_nisplus-2.8.solibc-2.8.so libnl-genl-3.a libnss_nisplus.so.2libcidn-2.8.solibnl-genl-3.la libnss_nis.so.2libcidn.so.1 libnl-genl-3.so libpcprofile.solibcrypt-2.8.so libnl-genl-3.so.200 libpthread-2.8.solibcrypto.a libnl-genl-3.so.200.18.0 libpthread.so.0libcrypto.so libnl-idiag-3.a libresolv-2.8.solibcrypto.so.1.0.0libnl-idiag-3.la libresolv.so.2libcrypt.so.1 libnl-idiag-3.so librt-2.8.solibc.so.6libnl-idiag-3.so.200 librt.so.1libdl-2.8.so libnl-idiag-3.so.200.18.0 libSegFault.solibdl.so.2 libnl-nf-3.alibssl.alibfreetype.a libnl-nf-3.la libssl.solibfreetype.lalibnl-nf-3.so libssl.so.1.0.0libfreetype.solibnl-nf-3.so.200libthread_db-1.0.solibfreetype.so.6 libnl-nf-3.so.200.18.0libthread_db.so.1libfreetype.so.6.9.0 libnl-route-3.a libutil-2.8.solibgcc_s.so libnl-route-3.la libutil.so.1libgcc_s.so.1 libnl-route-3.so libz.alibm-2.8.so libnl-route-3.so.200 pkgconfiglibmemusage.solibnl-route-3.so.200.18.0 turbojpeg.hlibm.so.6libnsl-2.8.so

那么原因就出在 src/drivers/drivers.mak 里了！ 肯定是编译时，-lnl-3 库没有包含进来。

然后，打开这个文件。

vi src/drivers/drivers.mk +31

发现下面这几句。

ifdef CONFIG_LIBNL32

DRV_LIBS += -lnl-3

DRV_LIBS += -lnl-genl-3

DRV_CFLAGS += -DCONFIG_LIBNL20 -I/usr/include/libnl3

那么我们只需要，在配置文件.config里，加 CONFIG_LIBNL32 = y 就可以了。