mipsel-openwrt-linux交叉編譯libwebsockets
1.下載libwebsockets
官網：https://libwebsockets.org/
GitHub源碼：
git clone https://libwebsockets.org/repo/libwebsockets
2.準備條件
交叉編譯完成zlib（可能不需要）和openssl，目前我還是使用的openssl，雖然它的代碼被很多人詬病，但是目前資料還是較多，暫時仍選用openssl。對於交叉編譯zlib和openssl在其它的總結上有說明，這裏不再細說。編譯安裝玩成後記得其目錄，後面要用。
3.編譯安裝libwebsockets
libwebsockets爲了跨平臺選擇使用cmake生成makefile，所以最好先了解一下cmake，對於編譯過libmysqlclient的人來說，cmake並不陌生。
解壓完libwebsockets源碼後，在其中創建mipsel文件夾，我們將安裝交叉編譯後的程序到該文件夾下。
git clone https://libwebsockets.org/repo/libwebsockets
cd libwebsockets
mkdir mipsel
cd mipsel
vim compile.sh簡單的編譯腳本：
#########################################################################
# File Name: compile.sh
# Author: loon
# mail: [email protected]
# Created Time: 2018年09月06日 星期四 09時37分51秒
#########################################################################
#!/bin/bash
cd ..
cmake \
-DCMAKE_INSTALL_PREFIX=/home/ubuntu/work/libwebsockets/mipsel \
-DCMAKE_C_COMPILER=mipsel-openwrt-linux-gcc-4.8.3 \
-DCMAKE_CXX_COMPILER=mipsel-openwrt-linux-g++ \
-DLWS_OPENSSL_INCLUDE_DIRS=/usr/local/ssl-mipsel/include \
-DLWS_OPENSSL_LIBRARIES="/usr/local/ssl-mipsel/lib/libssl.so;/usr/local/ssl-mipsel/lib/libcrypto.so"
#-DZLIB_INCLUDE_DIR=/home/ubuntu/work/zlib-1.2.8/mipsel/include \
#-DZLIB_LIBRARY=/home/ubuntu/work/zlib-1.2.8/mipsel/lib \
make
make install
對於cmake的參數需要結合源碼中的CMakeLists.txt和cmake的知識來確認，然後結合自己的交叉編譯器即可。這其中由於庫的不同版本肯定會遇到一些問題，這需要結合問題去解決，後面我將我遇到的一些問題進行了記錄。
4.常見問題
可能出現的錯誤1：
-- Build files have been written to: /home/ubuntu/work/libwebsockets
[ 1%] Building C object CMakeFiles/websockets.dir/lib/core/alloc.c.o
In file included from /home/ubuntu/work/libwebsockets/lib/core/private.h:134:0,
from /home/ubuntu/work/libwebsockets/lib/core/alloc.c:1:
/home/ubuntu/work/libwebsockets/include/libwebsockets.h:223:25: fatal error: openssl/ssl.h: No such file or directory
#include <openssl/ssl.h>
^
compilation terminated.
CMakeFiles/websockets.dir/build.make:62: recipe for target 'CMakeFiles/websockets.dir/lib/core/alloc.c.o' failed
make[2]: *** [CMakeFiles/websockets.dir/lib/core/alloc.c.o] Error 1
CMakeFiles/Makefile2:141: recipe for target 'CMakeFiles/websockets.dir/all' failed
make[1]: *** [CMakeFiles/websockets.dir/all] Error 2
Makefile:149: recipe for target 'all' failed
make: *** [all] Error 2
[ 1%] Building C object CMakeFiles/websockets.dir/lib/core/alloc.c.o
In file included from /home/ubuntu/work/libwebsockets/lib/core/private.h:134:0,
from /home/ubuntu/work/libwebsockets/lib/core/alloc.c:1:
/home/ubuntu/work/libwebsockets/include/libwebsockets.h:223:25: fatal error: openssl/ssl.h: No such file or directory
#include <openssl/ssl.h>
^
compilation terminated.
CMakeFiles/websockets.dir/build.make:62: recipe for target 'CMakeFiles/websockets.dir/lib/core/alloc.c.o' failed
make[2]: *** [CMakeFiles/websockets.dir/lib/core/alloc.c.o] Error 1
CMakeFiles/Makefile2:141: recipe for target 'CMakeFiles/websockets.dir/all' failed
make[1]: *** [CMakeFiles/websockets.dir/all] Error 2
Makefile:149: recipe for target 'all' failed
make: *** [all] Error 2編譯時遇到這種問題可以看到是沒有找到相關的openssl的頭文件，可能是沒有正確指明頭文件位置，或者cmake中的指定openssl頭文件的指令有誤。
可能出現的錯誤2：
[ 44%] Linking C executable bin/libwebsockets-test-fuzxy
lib/libwebsockets.a(ssl.c.o): In function `lws_ssl_get_error':
ssl.c:(.text+0x270): undefined reference to `SSL_get_error'
lib/libwebsockets.a(ssl.c.o): In function `lws_ssl_elaborate_error':
ssl.c:(.text+0x444): undefined reference to `ERR_error_string_n'
ssl.c:(.text+0x44c): undefined reference to `ERR_get_error'
lib/libwebsockets.a(ssl.c.o): In function `lws_ssl_bind_passphrase':
ssl.c:(.text+0x488): undefined reference to `SSL_CTX_set_default_passwd_cb_userdata'
ssl.c:(.text+0x4a4): undefined reference to `SSL_CTX_set_default_passwd_cb'
lib/libwebsockets.a(ssl.c.o): In function `lws_context_init_ssl_library':
ssl.c:(.text+0x4d8): undefined reference to `SSL_library_init'
ssl.c:(.text+0x4e0): undefined reference to `OPENSSL_add_all_algorithms_noconf'
ssl.c:(.text+0x4e8): undefined reference to `SSL_load_error_strings'
ssl.c:(.text+0x504): undefined reference to `SSL_get_ex_new_index'
ssl.c:(.text+0x524): undefined reference to `SSL_CTX_get_ex_new_index'
lib/libwebsockets.a(ssl.c.o): In function `lws_ssl_destroy':
ssl.c:(.text+0x574): undefined reference to `SSL_CTX_free'
ssl.c:(.text+0x5a0): undefined reference to `SSL_CTX_free'
ssl.c:(.text+0x5a8): undefined reference to `ERR_remove_thread_state'
ssl.c:(.text+0x5b0): undefined reference to `SSL_COMP_free_compression_methods'
ssl.c:(.text+0x5b8): undefined reference to `ERR_free_strings'
ssl.c:(.text+0x5c0): undefined reference to `EVP_cleanup'
ssl.c:(.text+0x5d0): undefined reference to `CRYPTO_cleanup_all_ex_data'
lib/libwebsockets.a(ssl.c.o): In function `lws_ssl_capable_read':
ssl.c:(.text+0x63c): undefined reference to `SSL_read'
ssl.c:(.text+0x6dc): undefined reference to `SSL_pending'這種情況明顯是沒有找到鏈接庫，我們結合config生成時的警告來進一步確定:
WARNING: Target "cmTC_2456e" requests linking to directory "/usr/local/ssl-mipsel/lib". Targets may link only to libraries. CMake is dropping the item.
-- Looking for SSL_CTX_set1_param - not found
-- Looking for SSL_set_info_callback
WARNING: Target "cmTC_b8022" requests linking to directory "/usr/local/ssl-mipsel/lib". Targets may link only to libraries. CMake is dropping the item.
-- Looking for SSL_set_info_callback - not found
-- Looking for X509_VERIFY_PARAM_set1_host
WARNING: Target "cmTC_7f323" requests linking to directory "/usr/local/ssl-mipsel/lib". Targets may link only to libraries. CMake is dropping the item.
-- Looking for X509_VERIFY_PARAM_set1_host - not found
-- Looking for RSA_set0_key
WARNING: Target "cmTC_92ac5" requests linking to directory "/usr/local/ssl-mipsel/lib". Targets may link only to libraries. CMake is dropping the item.
-- Looking for RSA_set0_key - not found
-- Looking for X509_get_key_usage可能前面會有類似這樣的警告產生，這是由於庫文件僅僅指明路徑還是不夠的，還需要指明具體的庫文件的名字，比如libssl.so等，需要指明具體的庫的名字（這算是對cmake不熟悉造成的一個比較低級的錯誤）。
應該是：
-DLWS_OPENSSL_LIBRARIES="/usr/local/ssl-mipsel/lib/libssl.so;/usr/local/ssl-mipsel/lib/libcrypto.so"
而不是：
-DLWS_OPENSSL_LIBRARIES=/usr/local/ssl-mipsel/lib可能出現的錯誤3：
-- Configuring incomplete, errors occurred!
See also "/home/ubuntu/work/libwebsockets/CMakeFiles/CMakeOutput.log".
See also "/home/ubuntu/work/libwebsockets/CMakeFiles/CMakeError.log".
CMake Error: Unable to open check cache file for write. /home/ubuntu/work/libwebsockets/CMakeFiles/cmake.check_cache
Makefile:1937: recipe for target 'cmake_check_build_system' failed
make: *** [cmake_check_build_system] Error 1目前不是很清楚什麼原因導致了cmake執行時出問題了，目前我的解決方法就是刪除源碼重新下載編譯。
5.最終結果
編譯安裝結果
解決完所有問題後執行我們的腳本就會自動完成配置cmake、編譯和安裝過程。
...
[ 81%] Building C object CMakeFiles/websockets_shared.dir/lib/tls/openssl/openssl-client.c.o
[ 82%] Building C object CMakeFiles/websockets_shared.dir/lib/misc/sha-1.c.o
[ 83%] Building C object CMakeFiles/websockets_shared.dir/lib/plat/unix/unix-caps.c.o
[ 84%] Building C object CMakeFiles/websockets_shared.dir/lib/plat/unix/unix-fds.c.o
[ 85%] Building C object CMakeFiles/websockets_shared.dir/lib/plat/unix/unix-file.c.o
[ 86%] Building C object CMakeFiles/websockets_shared.dir/lib/plat/unix/unix-misc.c.o
[ 87%] Building C object CMakeFiles/websockets_shared.dir/lib/plat/unix/unix-init.c.o
[ 88%] Building C object CMakeFiles/websockets_shared.dir/lib/plat/unix/unix-pipe.c.o
[ 89%] Building C object CMakeFiles/websockets_shared.dir/lib/plat/unix/unix-service.c.o
[ 90%] Building C object CMakeFiles/websockets_shared.dir/lib/plat/unix/unix-sockets.c.o
[ 91%] Building C object CMakeFiles/websockets_shared.dir/lib/roles/http/server/server.c.o
[ 92%] Building C object CMakeFiles/websockets_shared.dir/lib/roles/http/server/lws-spa.c.o
[ 93%] Building C object CMakeFiles/websockets_shared.dir/lib/event-libs/poll/poll.c.o
[ 94%] Building C object CMakeFiles/websockets_shared.dir/lib/misc/lejp.c.o
[ 95%] Building C object CMakeFiles/websockets_shared.dir/lib/roles/http/server/lejp-conf.c.o
[ 96%] Linking C shared library lib/libwebsockets.so
/usr/local/ssl-mipsel/lib/libcrypto.so: warning: gethostbyname is obsolescent, use getnameinfo() instead.
[ 96%] Built target websockets_shared
Scanning dependencies of target test-server-extpoll
[ 97%] Building C object CMakeFiles/test-server-extpoll.dir/test-apps/test-server.c.o
[ 98%] Linking C executable bin/libwebsockets-test-server-extpoll
/usr/local/ssl-mipsel/lib/libcrypto.so: warning: gethostbyname is obsolescent, use getnameinfo() instead.
[ 98%] Built target test-server-extpoll
Scanning dependencies of target test-server
[ 99%] Building C object CMakeFiles/test-server.dir/test-apps/test-server.c.o
[100%] Linking C executable bin/libwebsockets-test-server
/usr/local/ssl-mipsel/lib/libcrypto.so: warning: gethostbyname is obsolescent, use getnameinfo() instead.
[100%] Built target test-server
Install the project...
-- Install configuration: "Release"
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/lib/pkgconfig/libwebsockets.pc
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/lib/pkgconfig/libwebsockets_static.pc
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-http.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-adopt.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-network-helper.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-stats.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-service.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-sha1-base64.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-ws-state.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-purify.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-esp32.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-write.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-ring.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-logs.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-vfs.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-context-vhost.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-jwk.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-cgi.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-lejp.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-jws.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-client.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-x509.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-spa.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-ws-ext.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-protocols-plugins.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-plugin-generic-sessions.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-timeout-timer.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-misc.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-genhash.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-writeable.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-ws-close.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-genrsa.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-callbacks.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets/lws-threadpool.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/lib/libwebsockets.a
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/lws_config.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/include/lws-plugin-ssh.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/lib/libwebsockets.so.13
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/lib/libwebsockets.so
-- Set runtime path of "/home/ubuntu/work/libwebsockets/mipsel/lib/libwebsockets.so.13" to ""
-- Up-to-date: /home/ubuntu/work/libwebsockets/mipsel/include/libwebsockets.h
-- Up-to-date: /home/ubuntu/work/libwebsockets/mipsel/include/lws_config.h
-- Up-to-date: /home/ubuntu/work/libwebsockets/mipsel/include/lws-plugin-ssh.h
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/bin/libwebsockets-test-server
-- Set runtime path of "/home/ubuntu/work/libwebsockets/mipsel/bin/libwebsockets-test-server" to ""
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/bin/libwebsockets-test-fuzxy
-- Set runtime path of "/home/ubuntu/work/libwebsockets/mipsel/bin/libwebsockets-test-fuzxy" to ""
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/bin/libwebsockets-test-server-extpoll
-- Set runtime path of "/home/ubuntu/work/libwebsockets/mipsel/bin/libwebsockets-test-server-extpoll" to ""
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/bin/libwebsockets-test-lejp
-- Set runtime path of "/home/ubuntu/work/libwebsockets/mipsel/bin/libwebsockets-test-lejp" to ""
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/bin/libwebsockets-test-client
-- Set runtime path of "/home/ubuntu/work/libwebsockets/mipsel/bin/libwebsockets-test-client" to ""
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/libwebsockets-test-server.key.pem
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/libwebsockets-test-server.pem
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/favicon.ico
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/leaf.jpg
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/candide.zip
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/libwebsockets.org-logo.png
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/http2.png
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/wss-over-h2.png
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/lws-common.js
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/test.html
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/test.css
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/test.js
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/private/index.html
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/lws-ssh-test-keys
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/share/libwebsockets-test-server/lws-ssh-test-keys.pub
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/lib/cmake/libwebsockets/LibwebsocketsConfig.cmake
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/lib/cmake/libwebsockets/LibwebsocketsConfigVersion.cmake
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/lib/cmake/libwebsockets/LibwebsocketsTargets.cmake
-- Installing: /home/ubuntu/work/libwebsockets/mipsel/lib/cmake/libwebsockets/LibwebsocketsTargets-release.cmake在開發板上的測試結果
這是根據我們配置安裝後的mipsel目錄下的文件目錄樹：
ubuntu@ubuntu-virtual-machine:~/work/libwebsockets/mipsel$ tree -a
.
├── bin
│ ├── libwebsockets-test-client
│ ├── libwebsockets-test-fuzxy
│ ├── libwebsockets-test-lejp
│ ├── libwebsockets-test-server
│ └── libwebsockets-test-server-extpoll
├── compile.sh
├── include
│ ├── libwebsockets
│ │ ├── lws-adopt.h
│ │ ├── lws-callbacks.h
│ │ ├── lws-cgi.h
│ │ ├── lws-client.h
│ │ ├── lws-context-vhost.h
│ │ ├── lws-esp32.h
│ │ ├── lws-genhash.h
│ │ ├── lws-genrsa.h
│ │ ├── lws-http.h
│ │ ├── lws-jwk.h
│ │ ├── lws-jws.h
│ │ ├── lws-lejp.h
│ │ ├── lws-logs.h
│ │ ├── lws-misc.h
│ │ ├── lws-network-helper.h
│ │ ├── lws-plugin-generic-sessions.h
│ │ ├── lws-protocols-plugins.h
│ │ ├── lws-purify.h
│ │ ├── lws-ring.h
│ │ ├── lws-service.h
│ │ ├── lws-sha1-base64.h
│ │ ├── lws-spa.h
│ │ ├── lws-stats.h
│ │ ├── lws-threadpool.h
│ │ ├── lws-timeout-timer.h
│ │ ├── lws-vfs.h
│ │ ├── lws-writeable.h
│ │ ├── lws-write.h
│ │ ├── lws-ws-close.h
│ │ ├── lws-ws-ext.h
│ │ ├── lws-ws-state.h
│ │ └── lws-x509.h
│ ├── libwebsockets.h
│ ├── lws_config.h
│ └── lws-plugin-ssh.h
├── lib
│ ├── cmake
│ │ └── libwebsockets
│ │ ├── LibwebsocketsConfig.cmake
│ │ ├── LibwebsocketsConfigVersion.cmake
│ │ ├── LibwebsocketsTargets.cmake
│ │ └── LibwebsocketsTargets-release.cmake
│ ├── libwebsockets.a
│ ├── libwebsockets.so -> libwebsockets.so.13
│ ├── libwebsockets.so.13
│ └── pkgconfig
│ ├── libwebsockets.pc
│ └── libwebsockets_static.pc
└── share
└── libwebsockets-test-server
├── candide.zip
├── favicon.ico
├── http2.png
├── leaf.jpg
├── libwebsockets.org-logo.png
├── libwebsockets-test-server.key.pem
├── libwebsockets-test-server.pem
├── lws-common.js
├── lws-ssh-test-keys
├── lws-ssh-test-keys.pub
├── private
│ └── index.html
├── test.css
├── test.html
├── test.js
└── wss-over-h2.png
10 directories, 65 files將除過編譯文件的內容拷貝到網關中，我們就可以利用bin目錄下的測試服務程序等先測試一下編譯後的libwebsockets是否可以在我們的開發板上運行，測試通過則說明我們也可以利用該庫開發我們的wss程序。