LuaJIT ffi getaddrinfo

ms2008vip

用 LuaJIT 获取系统 IP

local ffi = require "ffi"
local C = ffi.C


ffi.cdef([[
struct ifaddrs {
   struct ifaddrs  *ifa_next;    /* Next item in list */
   char            *ifa_name;    /* Name of interface */
   unsigned int     ifa_flags;   /* Flags from SIOCGIFFLAGS */
   struct sockaddr *ifa_addr;    /* Address of interface */
   struct sockaddr *ifa_netmask; /* Netmask of interface */
   union {
       struct sockaddr *ifu_broadaddr;  /* Broadcast address of interface */
       struct sockaddr *ifu_dstaddr;    /* Point-to-point destination address */
   } ifa_ifu;
   void            *ifa_data;    /* Address-specific data */
};
// the union will be populated based on the following ifa_flags:
enum {
    IFF_BROADCAST   = 0x2,  /* broadcast address valid      */
    IFF_POINTOPOINT = 0x10  /* interface is has p-p link    */
};


int getifaddrs(struct ifaddrs **ifap);
void freeifaddrs(struct ifaddrs *ifa);


]])


-- Returns a Lua array of interfaces retrieved via C.getifaddrs
-- The original ifaddrs linked list is stored in ret.ifaddrs and is freed upon GC of ret
local function getifaddrs()
    local ifaddrs_root = ffi.new("struct ifaddrs *[1]")
    local res = C.getifaddrs( ifaddrs_root )
    assert( res == 0, ffi.errno() )


    -- convert linked list to Lua array for convenience
    local tret = {}
    local iter = ifaddrs_root[0]
    while iter ~= nil do
        tret[#tret + 1] = iter
        -- print(ffi.string(iter.ifa_name))
        if ffi.string(iter.ifa_name) ~= "lo" then
            print(ffi.string(iter.ifa_name), ffi.string(iter.ifa_addr))
        end
        iter = iter.ifa_next
    end


    -- free ifaddrs when tret is gc'd
    tret.ifaddrs = ifaddrs_root
    ffi.gc( ifaddrs_root, function(t) C.freeifaddrs(t[0]) end )
    return tret
end


getifaddrs()

目前的问题是 struct sockaddr 无法转换为 lua string，报

luajit: ffi_getaddrinfo.lua:42: bad argument #1 to 'string' (cannot convert 'struct sockaddr *' to 'const char *')

ms2008vip

@agentzh @doujiang

在 2017年5月22日星期一 UTC+8下午3:45:23，ms2008写道：

用 LuaJIT 获取系统 IP

local ffi = require "ffi" local C = ffi.C ffi.cdef([[ struct ifaddrs { struct ifaddrs *ifa_next; /* Next item in list */ char *ifa_name; /* Name of interface */ unsigned int ifa_flags; /* Flags from SIOCGIFFLAGS */ struct sockaddr *ifa_addr; /* Address of interface */ struct sockaddr *ifa_netmask; /* Netmask of interface */ union { struct sockaddr *ifu_broadaddr; /* Broadcast address of interface */ struct sockaddr *ifu_dstaddr; /* Point-to-point destination address */ } ifa_ifu; void *ifa_data; /* Address-specific data */ }; // the union will be populated based on the following ifa_flags: enum { IFF_BROADCAST = 0x2, /* broadcast address valid */ IFF_POINTOPOINT = 0x10 /* interface is has p-p link */ }; int getifaddrs(struct ifaddrs **ifap); void freeifaddrs(struct ifaddrs *ifa); ]]) -- Returns a Lua array of interfaces retrieved via C.getifaddrs -- The original ifaddrs linked list is stored in ret.ifaddrs and is freed upon GC of ret local function getifaddrs() local ifaddrs_root = ffi.new("struct ifaddrs *[1]") local res = C.getifaddrs( ifaddrs_root ) assert( res == 0, ffi.errno() ) -- convert linked list to Lua array for convenience local tret = {} local iter = ifaddrs_root[0] while iter ~= nil do tret[#tret + 1] = iter -- print(ffi.string(iter.ifa_name)) if ffi.string(iter.ifa_name) ~= "lo" then print(ffi.string(iter.ifa_name), ffi.string(iter.ifa_addr)) end iter = iter.ifa_next end -- free ifaddrs when tret is gc'd tret.ifaddrs = ifaddrs_root ffi.gc( ifaddrs_root, function(t) C.freeifaddrs(t[0]) end ) return tret end getifaddrs()

目前的问题是 struct sockaddr 无法转换为 lua string，报

luajit: ffi_getaddrinfo.lua:42: bad argument #1 to 'string' (cannot convert 'struct sockaddr *' to 'const char *')

detailyang

Hello.
认真看下错误，iter.ifa_addr 明明是 struct sockaddr *，怎么能随随便便转换为 const char *
呢，建议 man getifaddrs 仔细看看 EXAMPLE 下的 C 例子是如何吐出接口的地址。

       #include <arpa/inet.h>
       #include <sys/socket.h>
       #include <netdb.h>
       #include <ifaddrs.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>

       int
       main(int argc, char *argv[])
       {
           struct ifaddrs *ifaddr, *ifa;
           int family, s;
           char host[NI_MAXHOST];

           if (getifaddrs(&ifaddr) == -1) {
               perror("getifaddrs");
               exit(EXIT_FAILURE);
           }

           /* Walk through linked list, maintaining head pointer so we
              can free list later */

           for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
               if (ifa->ifa_addr == NULL)
                   continue;

               family = ifa->ifa_addr->sa_family;

               /* Display interface name and family (including symbolic
                  form of the latter for the common families) */

               printf("%s  address family: %d%s\n",
                       ifa->ifa_name, family,
                       (family == AF_PACKET) ? " (AF_PACKET)" :
                       (family == AF_INET) ?   " (AF_INET)" :
                       (family == AF_INET6) ?  " (AF_INET6)" : "");

               /* For an AF_INET* interface address, display the address */

               if (family == AF_INET || family == AF_INET6) {
                   s = getnameinfo(ifa->ifa_addr,
                           (family == AF_INET) ? sizeof(struct sockaddr_in) :
                                                 sizeof(struct sockaddr_in6),
                           host, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);
                   if (s != 0) {
                       printf("getnameinfo() failed: %s\n", gai_strerror(s));
                       exit(EXIT_FAILURE);
                   }
                   printf("\taddress: <%s>\n", host);
               }
           }

           freeifaddrs(ifaddr);
           exit(EXIT_SUCCESS);
       }

2017-05-23 16:07 GMT+08:00 ms2008 <ms20...@gmail.com>:
> @agentzh @doujiang
>
> 在 2017年5月22日星期一 UTC+8下午3:45:23，ms2008写道：
>>
>> 用 LuaJIT 获取系统 IP
>>
>> local ffi = require "ffi"
>> local C = ffi.C
>>
>>
>> ffi.cdef([[
>> struct ifaddrs {
>>    struct ifaddrs  *ifa_next;    /* Next item in list */
>>    char            *ifa_name;    /* Name of interface */
>>    unsigned int     ifa_flags;   /* Flags from SIOCGIFFLAGS */
>>    struct sockaddr *ifa_addr;    /* Address of interface */
>>    struct sockaddr *ifa_netmask; /* Netmask of interface */
>>    union {
>>        struct sockaddr *ifu_broadaddr;  /* Broadcast address of interface
>> */
>>        struct sockaddr *ifu_dstaddr;    /* Point-to-point destination
>> address */
>>    } ifa_ifu;
>>    void            *ifa_data;    /* Address-specific data */
>> };
>> // the union will be populated based on the following ifa_flags:
>> enum {
>>     IFF_BROADCAST   = 0x2,  /* broadcast address valid      */
>>     IFF_POINTOPOINT = 0x10  /* interface is has p-p link    */
>> };
>>
>>
>> int getifaddrs(struct ifaddrs **ifap);
>> void freeifaddrs(struct ifaddrs *ifa);
>>
>>
>> ]])
>>
>>
>> -- Returns a Lua array of interfaces retrieved via C.getifaddrs
>> -- The original ifaddrs linked list is stored in ret.ifaddrs and is freed
>> upon GC of ret
>> local function getifaddrs()
>>     local ifaddrs_root = ffi.new("struct ifaddrs *[1]")
>>     local res = C.getifaddrs( ifaddrs_root )
>>     assert( res == 0, ffi.errno() )
>>
>>
>>     -- convert linked list to Lua array for convenience
>>     local tret = {}
>>     local iter = ifaddrs_root[0]
>>     while iter ~= nil do
>>         tret[#tret + 1] = iter
>>         -- print(ffi.string(iter.ifa_name))
>>         if ffi.string(iter.ifa_name) ~= "lo" then
>>             print(ffi.string(iter.ifa_name), ffi.string(iter.ifa_addr))
>>         end
>>         iter = iter.ifa_next
>>     end
>>
>>
>>     -- free ifaddrs when tret is gc'd
>>     tret.ifaddrs = ifaddrs_root
>>     ffi.gc( ifaddrs_root, function(t) C.freeifaddrs(t[0]) end )
>>     return tret
>> end
>>
>>
>> getifaddrs()
>>
>> 目前的问题是 struct sockaddr 无法转换为 lua string， 报
>>
>> luajit: ffi_getaddrinfo.lua:42: bad argument #1 to 'string' (cannot
>> convert 'struct sockaddr *' to 'const char *')
>
> --
>

spacewanderlzx

提个有点离题的建议：
建议用 C 封装一层，然后暴露出简单类型的 API 给 LuaJIT 调用。

根据经验教训，系统头文件里面的结构体通常会大量采用宏去实现头文件兼容。由于 LuaJIT FFI 不支持宏，只能直接把这些结构体定义暴露到 Lua 代码里面，那是相当的恶心。
而且兼容性并不好。如果是用 C 实现的，当系统的 ABI 变化时，可能重新编译一遍就可以了。用 Lua 实现的话，需要直接改代码，而且缺乏可靠的方式去判断当前到底用的是哪套 ABI。

在 2017年5月22日星期一 UTC+8下午3:45:23，ms2008写道：

用 LuaJIT 获取系统 IP

local ffi = require "ffi" local C = ffi.C ffi.cdef([[ struct ifaddrs { struct ifaddrs *ifa_next; /* Next item in list */ char *ifa_name; /* Name of interface */ unsigned int ifa_flags; /* Flags from SIOCGIFFLAGS */ struct sockaddr *ifa_addr; /* Address of interface */ struct sockaddr *ifa_netmask; /* Netmask of interface */ union { struct sockaddr *ifu_broadaddr; /* Broadcast address of interface */ struct sockaddr *ifu_dstaddr; /* Point-to-point destination address */ } ifa_ifu; void *ifa_data; /* Address-specific data */ }; // the union will be populated based on the following ifa_flags: enum { IFF_BROADCAST = 0x2, /* broadcast address valid */ IFF_POINTOPOINT = 0x10 /* interface is has p-p link */ }; int getifaddrs(struct ifaddrs **ifap); void freeifaddrs(struct ifaddrs *ifa); ]]) -- Returns a Lua array of interfaces retrieved via C.getifaddrs -- The original ifaddrs linked list is stored in ret.ifaddrs and is freed upon GC of ret local function getifaddrs() local ifaddrs_root = ffi.new("struct ifaddrs *[1]") local res = C.getifaddrs( ifaddrs_root ) assert( res == 0, ffi.errno() ) -- convert linked list to Lua array for convenience local tret = {} local iter = ifaddrs_root[0] while iter ~= nil do tret[#tret + 1] = iter -- print(ffi.string(iter.ifa_name)) if ffi.string(iter.ifa_name) ~= "lo" then print(ffi.string(iter.ifa_name), ffi.string(iter.ifa_addr)) end iter = iter.ifa_next end -- free ifaddrs when tret is gc'd tret.ifaddrs = ifaddrs_root ffi.gc( ifaddrs_root, function(t) C.freeifaddrs(t[0]) end ) return tret end getifaddrs()

目前的问题是 struct sockaddr 无法转换为 lua string，报

luajit: ffi_getaddrinfo.lua:42: bad argument #1 to 'string' (cannot convert 'struct sockaddr *' to 'const char *')

ms2008vip

谢谢，找到了一个 Mashape 的解决方案

在 2017年5月25日星期四 UTC+8上午12:23:21，Zexuan Luo写道：

提个有点离题的建议：
建议用 C 封装一层，然后暴露出简单类型的 API 给 LuaJIT 调用。

根据经验教训，系统头文件里面的结构体通常会大量采用宏去实现头文件兼容。由于 LuaJIT FFI 不支持宏，只能直接把这些结构体定义暴露到 Lua 代码里面，那是相当的恶心。
而且兼容性并不好。如果是用 C 实现的，当系统的 ABI 变化时，可能重新编译一遍就可以了。用 Lua 实现的话，需要直接改代码，而且缺乏可靠的方式去判断当前到底用的是哪套 ABI。

在 2017年5月22日星期一 UTC+8下午3:45:23，ms2008写道：
用 LuaJIT 获取系统 IP

local ffi = require "ffi" local C = ffi.C ffi.cdef([[ struct ifaddrs { struct ifaddrs *ifa_next; /* Next item in list */ char *ifa_name; /* Name of interface */ unsigned int ifa_flags; /* Flags from SIOCGIFFLAGS */ struct sockaddr *ifa_addr; /* Address of interface */ struct sockaddr *ifa_netmask; /* Netmask of interface */ union { struct sockaddr *ifu_broadaddr; /* Broadcast address of interface */ struct sockaddr *ifu_dstaddr; /* Point-to-point destination address */ } ifa_ifu; void *ifa_data; /* Address-specific data */ }; // the union will be populated based on the following ifa_flags: enum { IFF_BROADCAST = 0x2, /* broadcast address valid */ IFF_POINTOPOINT = 0x10 /* interface is has p-p link */ }; int getifaddrs(struct ifaddrs **ifap); void freeifaddrs(struct ifaddrs *ifa); ]]) -- Returns a Lua array of interfaces retrieved via C.getifaddrs -- The original ifaddrs linked list is stored in ret.ifaddrs and is freed upon GC of ret local function getifaddrs() local ifaddrs_root = ffi.new("struct ifaddrs *[1]") local res = C.getifaddrs( ifaddrs_root ) assert( res == 0, ffi.errno() ) -- convert linked list to Lua array for convenience local tret = {} local iter = ifaddrs_root[0] while iter ~= nil do tret[#tret + 1] = iter -- print(ffi.string(iter.ifa_name)) if ffi.string(iter.ifa_name) ~= "lo" then print(ffi.string(iter.ifa_name), ffi.string(iter.ifa_addr)) end iter = iter.ifa_next end -- free ifaddrs when tret is gc'd tret.ifaddrs = ifaddrs_root ffi.gc( ifaddrs_root, function(t) C.freeifaddrs(t[0]) end ) return tret end getifaddrs()

目前的问题是 struct sockaddr 无法转换为 lua string，报

luajit: ffi_getaddrinfo.lua:42: bad argument #1 to 'string' (cannot convert 'struct sockaddr *' to 'const char *')

soul11201

2017-05-25 9:41 GMT+08:00 ms2008 <ms20...@gmail.com>:

谢谢，找到了一个 Mashape 的解决方案

也让我们学习下

：）

--

-----

http://blog.soul11201.com