Auto merge of #809 - djg:freebsd_sol_local, r=alexcrichton

Local peer credential support for FreeBSD.

FreeBSD uses SOL_SOCKET/LOCAL_PEERCRED instead of SOL_SOCKET/SO_PEERCRED parameters to getsocktopt to retrieve the credentials of a socket's peer.

(Documented in man 4 unix)

Author: bors

src/unix/bsd/freebsdlike/freebsd/mod.rs

@@ -127,6 +127,14 @@ s! {
         pub shm_dtime: ::time_t,
         pub shm_ctime: ::time_t,
     }
+
+    pub struct xucred {
+        pub cr_version: ::c_uint,
+        pub cr_uid: ::uid_t,
+        pub cr_ngroups: ::c_short,
+        pub cr_groups: [::gid_t;16],
+        __cr_unused1: *mut ::c_void,
+    }
 }
 
 pub const SIGEV_THREAD_ID: ::c_int = 4;
@@ -402,6 +410,11 @@ pub const SO_PROTOCOL: ::c_int = 0x1016;
 pub const SO_PROTOTYPE: ::c_int = SO_PROTOCOL;
 pub const SO_VENDOR: ::c_int = 0x80000000;
 
+pub const LOCAL_PEERCRED: ::c_int = 1;
+pub const LOCAL_CREDS: ::c_int = 2;
+pub const LOCAL_CONNWAIT: ::c_int = 4;
+pub const LOCAL_VENDOR: ::c_int = SO_VENDOR;
+
 pub const AF_SLOW: ::c_int = 33;
 pub const AF_SCLUSTER: ::c_int = 34;
 pub const AF_ARP: ::c_int = 35;
@@ -766,6 +779,9 @@ pub const _PC_ACL_NFS4: ::c_int = 64;
 
 pub const _SC_CPUSET_SIZE: ::c_int = 122;
 
+pub const XU_NGROUPS: ::c_int = 16;
+pub const XUCRED_VERSION: ::c_uint = 0;
+
 extern {
     pub fn __error() -> *mut ::c_int;