linux-user: Support for NETLINK socket options

This change includes support for all AF_NETLINK socket options up to about
kernel version 5.4 (5.4 is not formally released at the time of writing).
Socket options that were introduced in kernel versions before the oldest
currently stable kernel version are guarded by kernel version macros.

This change has been built under gcc 8.3, and clang 9.0, and it passes
`make check`. The netlink options have been tested by emulating some
non-trival software that uses NETLINK socket options, but they have
not been exaustively verified.

Signed-off-by: Josh Kunz <jkz@google.com>
Message-Id: <20191029224310.164025-1-jkz@google.com>
[lv: updated patch according to CODING_STYLE]
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

linux-user/syscall.c

@@ -2248,6 +2248,39 @@ static abi_long do_setsockopt(int sockfd, int level, int optname,
             return -TARGET_EFAULT;
 	ret = get_errno(setsockopt(sockfd, SOL_SOCKET, optname, &val, sizeof(val)));
         break;
+#ifdef SOL_NETLINK
+    case SOL_NETLINK:
+        switch (optname) {
+        case NETLINK_PKTINFO:
+        case NETLINK_ADD_MEMBERSHIP:
+        case NETLINK_DROP_MEMBERSHIP:
+        case NETLINK_BROADCAST_ERROR:
+        case NETLINK_NO_ENOBUFS:
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 2, 0)
+        case NETLINK_LISTEN_ALL_NSID:
+        case NETLINK_CAP_ACK:
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(4, 2, 0) */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 12, 0)
+        case NETLINK_EXT_ACK:
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(4, 12, 0) */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 20, 0)
+        case NETLINK_GET_STRICT_CHK:
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(4, 12, 0) */
+            break;
+        default:
+            goto unimplemented;
+        }
+        val = 0;
+        if (optlen < sizeof(uint32_t)) {
+            return -TARGET_EINVAL;
+        }
+        if (get_user_u32(val, optval_addr)) {
+            return -TARGET_EFAULT;
+        }
+        ret = get_errno(setsockopt(sockfd, SOL_NETLINK, optname, &val,
+                                   sizeof(val)));
+        break;
+#endif /* SOL_NETLINK */
     default:
     unimplemented:
         gemu_log("Unsupported setsockopt level=%d optname=%d\n", level, optname);
@@ -2532,6 +2565,74 @@ static abi_long do_getsockopt(int sockfd, int level, int optname,
             break;
         }
         break;
+#ifdef SOL_NETLINK
+    case SOL_NETLINK:
+        switch (optname) {
+        case NETLINK_PKTINFO:
+        case NETLINK_BROADCAST_ERROR:
+        case NETLINK_NO_ENOBUFS:
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 2, 0)
+        case NETLINK_LISTEN_ALL_NSID:
+        case NETLINK_CAP_ACK:
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(4, 2, 0) */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 12, 0)
+        case NETLINK_EXT_ACK:
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(4, 12, 0) */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 20, 0)
+        case NETLINK_GET_STRICT_CHK:
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(4, 12, 0) */
+            if (get_user_u32(len, optlen)) {
+                return -TARGET_EFAULT;
+            }
+            if (len != sizeof(val)) {
+                return -TARGET_EINVAL;
+            }
+            lv = len;
+            ret = get_errno(getsockopt(sockfd, level, optname, &val, &lv));
+            if (ret < 0) {
+                return ret;
+            }
+            if (put_user_u32(lv, optlen)
+                || put_user_u32(val, optval_addr)) {
+                return -TARGET_EFAULT;
+            }
+            break;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 2, 0)
+        case NETLINK_LIST_MEMBERSHIPS:
+        {
+            uint32_t *results;
+            int i;
+            if (get_user_u32(len, optlen)) {
+                return -TARGET_EFAULT;
+            }
+            if (len < 0) {
+                return -TARGET_EINVAL;
+            }
+            results = lock_user(VERIFY_WRITE, optval_addr, len, 1);
+            if (!results) {
+                return -TARGET_EFAULT;
+            }
+            lv = len;
+            ret = get_errno(getsockopt(sockfd, level, optname, results, &lv));
+            if (ret < 0) {
+                unlock_user(results, optval_addr, 0);
+                return ret;
+            }
+            /* swap host endianess to target endianess. */
+            for (i = 0; i < (len / sizeof(uint32_t)); i++) {
+                results[i] = tswap32(results[i]);
+            }
+            if (put_user_u32(lv, optlen)) {
+                return -TARGET_EFAULT;
+            }
+            unlock_user(results, optval_addr, 0);
+            break;
+        }
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(4, 2, 0) */
+        default:
+            goto unimplemented;
+        }
+#endif /* SOL_NETLINK */
     default:
     unimplemented:
         gemu_log("getsockopt level=%d optname=%d not yet supported\n",