start implementing our own limited equivalent to netifaces

setup.py

@@ -119,9 +119,6 @@ install_requires = [
     # Support for Python 3 transition
     "future >= 0.18.2",
 
-    # Discover local network configuration
-    "netifaces",
-
     # Utility code:
     "pyutil >= 3.3.0",
 

src/allmydata/util/_posix_netifaces.py

@@ -0,0 +1,98 @@
+
+from cffi import FFI
+from socket import inet_ntop, AF_INET, AF_INET6
+
+ffi = FFI()
+ffi.cdef("""
+struct in_addr {
+  union {
+    struct {
+      unsigned char s_b1;
+      unsigned char s_b2;
+      unsigned char s_b3;
+      unsigned char s_b4;
+    } S_un_b;
+    struct {
+      unsigned short s_w1;
+      unsigned short s_w2;
+    } S_un_w;
+    unsigned long S_addr;
+  } S_un;
+};
+
+struct in6_addr {
+        uint8_t  s6_addr[16];  /* IPv6 address */
+};
+
+struct sockaddr {
+        unsigned short  sa_family;
+        char            sa_data[14];
+};
+
+struct sockaddr_in {
+   unsigned short   sin_family;
+   unsigned short   sin_port;
+   struct in_addr   sin_addr;
+};
+
+struct sockaddr_in6 {
+       unsigned char    sin6_len;      /* length of this structure */
+       unsigned char    sin6_family;   /* AF_INET6                 */
+       uint16_t         sin6_port;     /* Transport layer port #   */
+       uint32_t         sin6_flowinfo; /* IPv6 flow information    */
+       struct in6_addr  sin6_addr;     /* IPv6 address             */
+};
+
+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 */
+};
+
+int getifaddrs(struct ifaddrs **ifap);
+void freeifaddrs(struct ifaddrs *ifa);
+""")
+_C = ffi.dlopen(None)
+
+def interfaces():
+    result = {}
+
+    # The memory allocated is garbage collected along with ifaddrs_p
+    ifaddrs_p = ffi.new("struct ifaddrs**")
+
+    errno = _C.getifaddrs(ifaddrs_p)
+    if errno == 0:
+        try:
+            # Success, read the values.
+            ifaddr = ifaddrs_p[0]
+            while ifaddr != ffi.NULL:
+                addr = _sockaddr_to_address(ifaddr.ifa_addr)
+                if addr is not None:
+                    result.setdefault(ffi.string(ifaddr.ifa_name), []).append(addr)
+                ifaddr = ifaddr.ifa_next
+        finally:
+            # The ifaddrs structs themselves are dynamically allocated by
+            # getifaddrs and need to be freed.
+            _C.freeifaddrs(ifaddrs_p[0])
+    else:
+        raise OSError(errno)
+
+    return result
+
+
+def _sockaddr_to_address(sockaddr):
+    if sockaddr.sa_family == AF_INET:
+        sockaddr_x = ffi.cast("struct sockaddr_in*", sockaddr)
+        offset = 4
+        size = 4
+    elif sockaddr.sa_family == AF_INET6:
+        sockaddr_x = ffi.cast("struct sockaddr_in6*", sockaddr)
+        offset = 8
+        size = 16
+    else:
+        return None
+
+    buf = ffi.buffer(sockaddr_x, offset + size)[offset:offset + size]
+    return inet_ntop(sockaddr.sa_family, buf)

src/allmydata/util/iputil.py

@@ -19,7 +19,7 @@ from zope.interface import implementer
 
 import attr
 
-from netifaces import (
+from .netifaces import (
     interfaces,
     ifaddresses,
 )

src/allmydata/util/netifaces.py

@@ -0,0 +1,12 @@
+
+__all__ = [
+    "interfaces",
+]
+
+from twisted.python.runtime import platform
+
+if platform.isWindows():
+    from ._windows_netifaces import interfaces
+else:
+    from ._posix_netifaces import interfaces
+