[PATCH 4/4] netlink: Introduce a helper function to simplify netlink functions

Shi Lei posted 4 patches 5 years, 1 month ago
There is a newer version of this series
[PATCH 4/4] netlink: Introduce a helper function to simplify netlink functions
Posted by Shi Lei 5 years, 1 month ago
Extract common code as helper function virNetlinkTalk, then simplify
the functions virNetlink[DumpLink|NewLink|DelLink|GetNeighbor].

Signed-off-by: Shi Lei <shi_lei@massclouds.com>
---
 src/util/virnetlink.c | 210 +++++++++++++++---------------------------
 src/util/virnetlink.h |   4 +-
 2 files changed, 78 insertions(+), 136 deletions(-)

diff --git a/src/util/virnetlink.c b/src/util/virnetlink.c
index fdcb0dc0..7bea38c0 100644
--- a/src/util/virnetlink.c
+++ b/src/util/virnetlink.c
@@ -353,6 +353,48 @@ int virNetlinkCommand(struct nl_msg *nl_msg,
     return 0;
 }
 
+
+static int
+virNetlinkTalk(const char *ifname,
+               virNetlinkMsg *nl_msg,
+               uint32_t src_pid,
+               uint32_t dst_pid,
+               struct nlmsghdr **resp,
+               unsigned int *resp_len,
+               int *error,
+               virNetlinkTalkFallback fallback)
+{
+    if (virNetlinkCommand(nl_msg, resp, resp_len,
+                          src_pid, dst_pid, NETLINK_ROUTE, 0) < 0)
+        return -1;
+
+    if (*resp_len < NLMSG_LENGTH(0) || resp == NULL)
+        goto malformed_resp;
+
+    if ((*resp)->nlmsg_type == NLMSG_ERROR) {
+        struct nlmsgerr *err = (struct nlmsgerr *) NLMSG_DATA(resp);
+        if ((*resp)->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
+            goto malformed_resp;
+
+        if (-err->error == EOPNOTSUPP && fallback)
+            return fallback(ifname);
+
+        if (err->error < 0) {
+            if (error)
+                *error = err->error;
+            return -1;
+        }
+    }
+
+    return 0;
+
+ malformed_resp:
+    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                   _("malformed netlink response message"));
+    return -1;
+}
+
+
 int
 virNetlinkDumpCommand(struct nl_msg *nl_msg,
                       virNetlinkDumpCallback callback,
@@ -396,6 +438,7 @@ virNetlinkDumpCommand(struct nl_msg *nl_msg,
     return 0;
 }
 
+
 /**
  * virNetlinkDumpLink:
  *
@@ -420,15 +463,13 @@ virNetlinkDumpLink(const char *ifname, int ifindex,
                    void **nlData, struct nlattr **tb,
                    uint32_t src_pid, uint32_t dst_pid)
 {
-    int rc = -1;
-    struct nlmsgerr *err;
     struct ifinfomsg ifinfo = {
         .ifi_family = AF_UNSPEC,
         .ifi_index  = ifindex
     };
-    unsigned int recvbuflen;
     g_autoptr(virNetlinkMsg) nl_msg = NULL;
     g_autofree struct nlmsghdr *resp = NULL;
+    unsigned int resp_len = 0;
 
     if (ifname && ifindex <= 0 && virNetDevGetIndex(ifname, &ifindex) < 0)
         return -1;
@@ -459,46 +500,19 @@ virNetlinkDumpLink(const char *ifname, int ifindex,
     }
 # endif
 
-    if (virNetlinkCommand(nl_msg, &resp, &recvbuflen,
-                          src_pid, dst_pid, NETLINK_ROUTE, 0) < 0)
+    if (virNetlinkTalk(ifname, nl_msg, src_pid, dst_pid,
+                       &resp, &resp_len, NULL, NULL) < 0)
         return -1;
 
-    if (recvbuflen < NLMSG_LENGTH(0) || resp == NULL)
-        goto malformed_resp;
-
-    switch (resp->nlmsg_type) {
-    case NLMSG_ERROR:
-        err = (struct nlmsgerr *)NLMSG_DATA(resp);
-        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
-            goto malformed_resp;
-
-        if (err->error) {
-            virReportSystemError(-err->error,
-                                 _("error dumping %s (%d) interface"),
-                                 ifname, ifindex);
-            return -1;
-        }
-        break;
-
-    case GENL_ID_CTRL:
-    case NLMSG_DONE:
-        rc = nlmsg_parse(resp, sizeof(struct ifinfomsg),
-                         tb, IFLA_MAX, NULL);
-        if (rc < 0)
-            goto malformed_resp;
-        break;
-
-    default:
-        goto malformed_resp;
+    if ((resp->nlmsg_type != GENL_ID_CTRL && resp->nlmsg_type != NLMSG_DONE) ||
+        nlmsg_parse(resp, sizeof(struct ifinfomsg), tb, IFLA_MAX, NULL) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("malformed netlink response message"));
+        return -1;
     }
 
     *nlData = g_steal_pointer(&resp);
     return 0;
-
- malformed_resp:
-    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
-                   _("malformed netlink response message"));
-    return rc;
 }
 
 
@@ -523,13 +537,12 @@ virNetlinkNewLink(const char *ifname,
                   virNetlinkNewLinkDataPtr extra_args,
                   int *error)
 {
-    struct nlmsgerr *err;
     struct nlattr *linkinfo = NULL;
     struct nlattr *infodata = NULL;
-    unsigned int buflen;
     struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
     g_autoptr(virNetlinkMsg) nl_msg = NULL;
     g_autofree struct nlmsghdr *resp = NULL;
+    unsigned int resp_len = 0;
 
     *error = 0;
 
@@ -591,37 +604,17 @@ virNetlinkNewLink(const char *ifname,
         }
     }
 
-    if (virNetlinkCommand(nl_msg, &resp, &buflen, 0, 0, NETLINK_ROUTE, 0) < 0)
+    if (virNetlinkTalk(ifname, nl_msg, 0, 0,
+                       &resp, &resp_len, error, NULL) < 0)
         return -1;
 
-    if (buflen < NLMSG_LENGTH(0) || resp == NULL)
-        goto malformed_resp;
-
-    switch (resp->nlmsg_type) {
-    case NLMSG_ERROR:
-        err = (struct nlmsgerr *)NLMSG_DATA(resp);
-        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
-            goto malformed_resp;
-
-        if (err->error < 0) {
-            *error = err->error;
-            return -1;
-        }
-        break;
-
-    case NLMSG_DONE:
-        break;
-
-    default:
-        goto malformed_resp;
+    if (resp->nlmsg_type != NLMSG_DONE) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("malformed netlink response message"));
+        return -1;
     }
 
     return 0;
-
- malformed_resp:
-    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
-                   _("malformed netlink response message"));
-    return -1;
 }
 
 
@@ -641,13 +634,12 @@ virNetlinkNewLink(const char *ifname,
  * Returns 0 on success, -1 on fatal error.
  */
 int
-virNetlinkDelLink(const char *ifname, virNetlinkDelLinkFallback fallback)
+virNetlinkDelLink(const char *ifname, virNetlinkTalkFallback fallback)
 {
-    struct nlmsgerr *err;
     struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
-    unsigned int recvbuflen;
     g_autoptr(virNetlinkMsg) nl_msg = NULL;
     g_autofree struct nlmsghdr *resp = NULL;
+    unsigned int resp_len = 0;
 
     nl_msg = nlmsg_alloc_simple(RTM_DELLINK, NLM_F_REQUEST);
     if (!nl_msg) {
@@ -659,44 +651,17 @@ virNetlinkDelLink(const char *ifname, virNetlinkDelLinkFallback fallback)
 
     NETLINK_MSG_PUT(nl_msg, IFLA_IFNAME, (strlen(ifname) + 1), ifname);
 
-    if (virNetlinkCommand(nl_msg, &resp, &recvbuflen, 0, 0,
-                          NETLINK_ROUTE, 0) < 0) {
+    if (virNetlinkTalk(ifname, nl_msg, 0, 0,
+                       &resp, &resp_len, NULL, fallback) < 0)
         return -1;
-    }
 
-    if (recvbuflen < NLMSG_LENGTH(0) || resp == NULL)
-        goto malformed_resp;
-
-    switch (resp->nlmsg_type) {
-    case NLMSG_ERROR:
-        err = (struct nlmsgerr *)NLMSG_DATA(resp);
-        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
-            goto malformed_resp;
-
-        if (-err->error == EOPNOTSUPP && fallback)
-            return fallback(ifname);
-
-        if (err->error) {
-            virReportSystemError(-err->error,
-                                 _("error destroying network device %s"),
-                                 ifname);
-            return -1;
-        }
-        break;
-
-    case NLMSG_DONE:
-        break;
-
-    default:
-        goto malformed_resp;
+    if (resp->nlmsg_type != NLMSG_DONE) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("malformed netlink response message"));
+        return -1;
     }
 
     return 0;
-
- malformed_resp:
-    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
-                   _("malformed netlink response message"));
-    return -1;
 }
 
 /**
@@ -712,18 +677,17 @@ virNetlinkDelLink(const char *ifname, virNetlinkDelLinkFallback fallback)
  *
  * Get neighbor table entry from netlink.
  *
- * Returns 0 on success, -1 on fatal error.
+ * Returns length of the raw data from netlink on success, -1 on fatal error.
  */
 int
 virNetlinkGetNeighbor(void **nlData, uint32_t src_pid, uint32_t dst_pid)
 {
-    struct nlmsgerr *err;
     struct ndmsg ndinfo = {
         .ndm_family = AF_UNSPEC,
     };
-    unsigned int recvbuflen;
     g_autoptr(virNetlinkMsg) nl_msg = NULL;
     g_autofree struct nlmsghdr *resp = NULL;
+    unsigned int resp_len = 0;
 
     nl_msg = nlmsg_alloc_simple(RTM_GETNEIGH, NLM_F_DUMP | NLM_F_REQUEST);
     if (!nl_msg) {
@@ -733,40 +697,18 @@ virNetlinkGetNeighbor(void **nlData, uint32_t src_pid, uint32_t dst_pid)
 
     NETLINK_MSG_APPEND(nl_msg, sizeof(ndinfo), &ndinfo);
 
-    if (virNetlinkCommand(nl_msg, &resp, &recvbuflen,
-                          src_pid, dst_pid, NETLINK_ROUTE, 0) < 0)
+    if (virNetlinkTalk(NULL, nl_msg, src_pid, dst_pid,
+                       &resp, &resp_len, NULL, NULL) < 0)
         return -1;
 
-    if (recvbuflen < NLMSG_LENGTH(0) || resp == NULL)
-        goto malformed_resp;
-
-    switch (resp->nlmsg_type) {
-    case NLMSG_ERROR:
-        err = (struct nlmsgerr *)NLMSG_DATA(resp);
-        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
-            goto malformed_resp;
-
-        if (err->error) {
-            virReportSystemError(-err->error,
-                                 "%s", _("error dumping"));
-            return -1;
-        }
-        break;
-
-    case RTM_NEWNEIGH:
-        break;
-
-    default:
-        goto malformed_resp;
+    if (resp->nlmsg_type != RTM_NEWNEIGH) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("malformed netlink response message"));
+        return -1;
     }
 
     *nlData = g_steal_pointer(&resp);
-    return recvbuflen;
-
- malformed_resp:
-    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
-                   _("malformed netlink response message"));
-    return -1;
+    return resp_len;
 }
 
 int
@@ -1300,7 +1242,7 @@ virNetlinkDumpLink(const char *ifname G_GNUC_UNUSED,
 
 int
 virNetlinkDelLink(const char *ifname G_GNUC_UNUSED,
-                  virNetlinkDelLinkFallback fallback G_GNUC_UNUSED)
+                  virNetlinkTalkFallback fallback G_GNUC_UNUSED)
 {
     virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _(unsupported));
     return -1;
diff --git a/src/util/virnetlink.h b/src/util/virnetlink.h
index 966d6db3..cab685fe 100644
--- a/src/util/virnetlink.h
+++ b/src/util/virnetlink.h
@@ -69,9 +69,9 @@ int virNetlinkNewLink(const char *ifname,
                       virNetlinkNewLinkDataPtr data,
                       int *error);
 
-typedef int (*virNetlinkDelLinkFallback)(const char *ifname);
+typedef int (*virNetlinkTalkFallback)(const char *ifname);
 
-int virNetlinkDelLink(const char *ifname, virNetlinkDelLinkFallback fallback);
+int virNetlinkDelLink(const char *ifname, virNetlinkTalkFallback fallback);
 
 int virNetlinkGetErrorCode(struct nlmsghdr *resp, unsigned int recvbuflen);
 
-- 
2.25.1


Re: [PATCH 4/4] netlink: Introduce a helper function to simplify netlink functions
Posted by Michal Privoznik 5 years, 1 month ago
On 12/21/20 4:23 AM, Shi Lei wrote:
> Extract common code as helper function virNetlinkTalk, then simplify
> the functions virNetlink[DumpLink|NewLink|DelLink|GetNeighbor].
> 
> Signed-off-by: Shi Lei <shi_lei@massclouds.com>
> ---
>   src/util/virnetlink.c | 210 +++++++++++++++---------------------------
>   src/util/virnetlink.h |   4 +-
>   2 files changed, 78 insertions(+), 136 deletions(-)

Nice cleanup. Patches 1-3 look good.

> 
> diff --git a/src/util/virnetlink.c b/src/util/virnetlink.c
> index fdcb0dc0..7bea38c0 100644
> --- a/src/util/virnetlink.c
> +++ b/src/util/virnetlink.c
> @@ -353,6 +353,48 @@ int virNetlinkCommand(struct nl_msg *nl_msg,
>       return 0;
>   }
>   
> +
> +static int
> +virNetlinkTalk(const char *ifname,
> +               virNetlinkMsg *nl_msg,
> +               uint32_t src_pid,
> +               uint32_t dst_pid,
> +               struct nlmsghdr **resp,
> +               unsigned int *resp_len,
> +               int *error,
> +               virNetlinkTalkFallback fallback)
> +{
> +    if (virNetlinkCommand(nl_msg, resp, resp_len,
> +                          src_pid, dst_pid, NETLINK_ROUTE, 0) < 0)
> +        return -1;
> +
> +    if (*resp_len < NLMSG_LENGTH(0) || resp == NULL)
> +        goto malformed_resp;
> +
> +    if ((*resp)->nlmsg_type == NLMSG_ERROR) {
> +        struct nlmsgerr *err = (struct nlmsgerr *) NLMSG_DATA(resp);
> +        if ((*resp)->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
> +            goto malformed_resp;
> +
> +        if (-err->error == EOPNOTSUPP && fallback)
> +            return fallback(ifname);
> +
> +        if (err->error < 0) {
> +            if (error)
> +                *error = err->error;

I wonder whether we should report an error here. I mean, if err->error 
is set (and not EOPNOTSUPP) then it's stored into *error, good. But -1 
is returned ...

> +            return -1;

.. here and it's indistinguishable to the caller from -1 returned in 
'malformed_resp'. Looking at the usage in next hunks, how about:

   if (error)
     *error = err->error;
   else
     virReportSystemError(-err->error, ...);

   return -1;

> +        }
> +    }
> +
> +    return 0;
> +
> + malformed_resp:
> +    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                   _("malformed netlink response message"));
> +    return -1;
> +}
> +
> +
>   int
>   virNetlinkDumpCommand(struct nl_msg *nl_msg,
>                         virNetlinkDumpCallback callback,
> @@ -396,6 +438,7 @@ virNetlinkDumpCommand(struct nl_msg *nl_msg,
>       return 0;
>   }
>   
> +
>   /**
>    * virNetlinkDumpLink:
>    *
> @@ -420,15 +463,13 @@ virNetlinkDumpLink(const char *ifname, int ifindex,
>                      void **nlData, struct nlattr **tb,
>                      uint32_t src_pid, uint32_t dst_pid)
>   {
> -    int rc = -1;
> -    struct nlmsgerr *err;
>       struct ifinfomsg ifinfo = {
>           .ifi_family = AF_UNSPEC,
>           .ifi_index  = ifindex
>       };
> -    unsigned int recvbuflen;
>       g_autoptr(virNetlinkMsg) nl_msg = NULL;
>       g_autofree struct nlmsghdr *resp = NULL;
> +    unsigned int resp_len = 0;
>   
>       if (ifname && ifindex <= 0 && virNetDevGetIndex(ifname, &ifindex) < 0)
>           return -1;
> @@ -459,46 +500,19 @@ virNetlinkDumpLink(const char *ifname, int ifindex,
>       }
>   # endif
>   
> -    if (virNetlinkCommand(nl_msg, &resp, &recvbuflen,
> -                          src_pid, dst_pid, NETLINK_ROUTE, 0) < 0)
> +    if (virNetlinkTalk(ifname, nl_msg, src_pid, dst_pid,
> +                       &resp, &resp_len, NULL, NULL) < 0)
>           return -1;
>   
> -    if (recvbuflen < NLMSG_LENGTH(0) || resp == NULL)
> -        goto malformed_resp;
> -
> -    switch (resp->nlmsg_type) {
> -    case NLMSG_ERROR:
> -        err = (struct nlmsgerr *)NLMSG_DATA(resp);
> -        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
> -            goto malformed_resp;
> -
> -        if (err->error) {
> -            virReportSystemError(-err->error,
> -                                 _("error dumping %s (%d) interface"),
> -                                 ifname, ifindex);


Here we'd report an error.

> -            return -1;
> -        }
> -        break;
> -
> -    case GENL_ID_CTRL:
> -    case NLMSG_DONE:
> -        rc = nlmsg_parse(resp, sizeof(struct ifinfomsg),
> -                         tb, IFLA_MAX, NULL);
> -        if (rc < 0)
> -            goto malformed_resp;
> -        break;
> -
> -    default:
> -        goto malformed_resp;
> +    if ((resp->nlmsg_type != GENL_ID_CTRL && resp->nlmsg_type != NLMSG_DONE) ||
> +        nlmsg_parse(resp, sizeof(struct ifinfomsg), tb, IFLA_MAX, NULL) < 0) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                       _("malformed netlink response message"));
> +        return -1;
>       }
>   
>       *nlData = g_steal_pointer(&resp);
>       return 0;
> -
> - malformed_resp:
> -    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> -                   _("malformed netlink response message"));
> -    return rc;
>   }
>   
>   
> @@ -523,13 +537,12 @@ virNetlinkNewLink(const char *ifname,
>                     virNetlinkNewLinkDataPtr extra_args,
>                     int *error)
>   {
> -    struct nlmsgerr *err;
>       struct nlattr *linkinfo = NULL;
>       struct nlattr *infodata = NULL;
> -    unsigned int buflen;
>       struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
>       g_autoptr(virNetlinkMsg) nl_msg = NULL;
>       g_autofree struct nlmsghdr *resp = NULL;
> +    unsigned int resp_len = 0;
>   
>       *error = 0;
>   
> @@ -591,37 +604,17 @@ virNetlinkNewLink(const char *ifname,
>           }
>       }
>   
> -    if (virNetlinkCommand(nl_msg, &resp, &buflen, 0, 0, NETLINK_ROUTE, 0) < 0)
> +    if (virNetlinkTalk(ifname, nl_msg, 0, 0,
> +                       &resp, &resp_len, error, NULL) < 0)
>           return -1;
>   
> -    if (buflen < NLMSG_LENGTH(0) || resp == NULL)
> -        goto malformed_resp;
> -
> -    switch (resp->nlmsg_type) {
> -    case NLMSG_ERROR:
> -        err = (struct nlmsgerr *)NLMSG_DATA(resp);
> -        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
> -            goto malformed_resp;
> -
> -        if (err->error < 0) {
> -            *error = err->error;
> -            return -1;

But here we wouldn't.

> -        }
> -        break;
> -
> -    case NLMSG_DONE:
> -        break;
> -
> -    default:
> -        goto malformed_resp;
> +    if (resp->nlmsg_type != NLMSG_DONE) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                       _("malformed netlink response message"));
> +        return -1;
>       }
>   
>       return 0;
> -
> - malformed_resp:
> -    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> -                   _("malformed netlink response message"));
> -    return -1;
>   }
>   
>   
> @@ -641,13 +634,12 @@ virNetlinkNewLink(const char *ifname,
>    * Returns 0 on success, -1 on fatal error.
>    */
>   int
> -virNetlinkDelLink(const char *ifname, virNetlinkDelLinkFallback fallback)
> +virNetlinkDelLink(const char *ifname, virNetlinkTalkFallback fallback)
>   {
> -    struct nlmsgerr *err;
>       struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
> -    unsigned int recvbuflen;
>       g_autoptr(virNetlinkMsg) nl_msg = NULL;
>       g_autofree struct nlmsghdr *resp = NULL;
> +    unsigned int resp_len = 0;
>   
>       nl_msg = nlmsg_alloc_simple(RTM_DELLINK, NLM_F_REQUEST);
>       if (!nl_msg) {
> @@ -659,44 +651,17 @@ virNetlinkDelLink(const char *ifname, virNetlinkDelLinkFallback fallback)
>   
>       NETLINK_MSG_PUT(nl_msg, IFLA_IFNAME, (strlen(ifname) + 1), ifname);
>   
> -    if (virNetlinkCommand(nl_msg, &resp, &recvbuflen, 0, 0,
> -                          NETLINK_ROUTE, 0) < 0) {
> +    if (virNetlinkTalk(ifname, nl_msg, 0, 0,
> +                       &resp, &resp_len, NULL, fallback) < 0)
>           return -1;
> -    }
>   
> -    if (recvbuflen < NLMSG_LENGTH(0) || resp == NULL)
> -        goto malformed_resp;
> -
> -    switch (resp->nlmsg_type) {
> -    case NLMSG_ERROR:
> -        err = (struct nlmsgerr *)NLMSG_DATA(resp);
> -        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
> -            goto malformed_resp;
> -
> -        if (-err->error == EOPNOTSUPP && fallback)
> -            return fallback(ifname);
> -
> -        if (err->error) {
> -            virReportSystemError(-err->error,
> -                                 _("error destroying network device %s"),
> -                                 ifname);


And here we would report an error again.

> -            return -1;
> -        }
> -        break;
> -
> -    case NLMSG_DONE:
> -        break;
> -
> -    default:
> -        goto malformed_resp;
> +    if (resp->nlmsg_type != NLMSG_DONE) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                       _("malformed netlink response message"));
> +        return -1;
>       }
>   
>       return 0;
> -
> - malformed_resp:
> -    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> -                   _("malformed netlink response message"));
> -    return -1;
>   }
>   
>   /**
> @@ -712,18 +677,17 @@ virNetlinkDelLink(const char *ifname, virNetlinkDelLinkFallback fallback)
>    *
>    * Get neighbor table entry from netlink.
>    *
> - * Returns 0 on success, -1 on fatal error.
> + * Returns length of the raw data from netlink on success, -1 on fatal error.
>    */
>   int
>   virNetlinkGetNeighbor(void **nlData, uint32_t src_pid, uint32_t dst_pid)
>   {
> -    struct nlmsgerr *err;
>       struct ndmsg ndinfo = {
>           .ndm_family = AF_UNSPEC,
>       };
> -    unsigned int recvbuflen;
>       g_autoptr(virNetlinkMsg) nl_msg = NULL;
>       g_autofree struct nlmsghdr *resp = NULL;
> +    unsigned int resp_len = 0;
>   
>       nl_msg = nlmsg_alloc_simple(RTM_GETNEIGH, NLM_F_DUMP | NLM_F_REQUEST);
>       if (!nl_msg) {
> @@ -733,40 +697,18 @@ virNetlinkGetNeighbor(void **nlData, uint32_t src_pid, uint32_t dst_pid)
>   
>       NETLINK_MSG_APPEND(nl_msg, sizeof(ndinfo), &ndinfo);
>   
> -    if (virNetlinkCommand(nl_msg, &resp, &recvbuflen,
> -                          src_pid, dst_pid, NETLINK_ROUTE, 0) < 0)
> +    if (virNetlinkTalk(NULL, nl_msg, src_pid, dst_pid,
> +                       &resp, &resp_len, NULL, NULL) < 0)
>           return -1;
>   
> -    if (recvbuflen < NLMSG_LENGTH(0) || resp == NULL)
> -        goto malformed_resp;
> -
> -    switch (resp->nlmsg_type) {
> -    case NLMSG_ERROR:
> -        err = (struct nlmsgerr *)NLMSG_DATA(resp);
> -        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
> -            goto malformed_resp;
> -
> -        if (err->error) {
> -            virReportSystemError(-err->error,
> -                                 "%s", _("error dumping"));
> -            return -1;

Ditto.

> -        }
> -        break;
> -
> -    case RTM_NEWNEIGH:
> -        break;
> -
> -    default:
> -        goto malformed_resp;
> +    if (resp->nlmsg_type != RTM_NEWNEIGH) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                       _("malformed netlink response message"));
> +        return -1;
>       }
>   
>       *nlData = g_steal_pointer(&resp);
> -    return recvbuflen;
> -
> - malformed_resp:
> -    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> -                   _("malformed netlink response message"));
> -    return -1;
> +    return resp_len;
>   }
>   

Michal