libnetwork: Properly handle errors from netlink messages

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

diff --git a/configure.ac b/configure.ac
index cc5b21e106f85d36e35c5225c1e1da6dbcfbba9a..7cb5ef1110fa393606d66f9b215fd61f2940b474 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -98,6 +98,7 @@ AC_SUBST([OUR_LDFLAGS], $with_ldflags)
 AC_CHECK_HEADERS_ONCE([
        ctype.h
        errno.h
+       linux/netlink.h
        net/if.h
        stdarg.h
        stdio.h

diff --git a/src/libnetwork/libnetwork.c b/src/libnetwork/libnetwork.c
index 65faa932a264ab25c2acd535f85aed0be336011e..17169b3e41d32659e741892eaf77de25240e3fbe 100644 (file)
--- a/src/libnetwork/libnetwork.c
+++ b/src/libnetwork/libnetwork.c
@@ -20,6 +20,7 @@
 
 #include <ctype.h>
 #include <errno.h>
+#include <linux/netlink.h>
 #include <linux/nl80211.h>
 #include <netlink/genl/ctrl.h>
 #include <netlink/genl/genl.h>
@@ -214,30 +215,74 @@ struct nl_msg* network_make_netlink_message(struct network_ctx* ctx,
        return msg;
 }
 
+struct network_netlink_message_status {
+       struct network_ctx* ctx;
+       int r;
+};
+
 static int __nl_ack_handler(struct nl_msg* msg, void* data) {
-       int* r = data;
-       *r = 0;
+       struct network_netlink_message_status* status = data;
+       status->r = 0;
 
        return NL_STOP;
 }
 
 static int __nl_finish_handler(struct nl_msg* msg, void* data) {
-       int* r = data;
-       *r = 0;
+       struct network_netlink_message_status* status = data;
+       status->r = 0;
 
        return NL_SKIP;
 }
 
+static int __nl_error_handler(struct sockaddr_nl* nla, struct nlmsgerr* err, void* data) {
+       struct network_netlink_message_status* status = data;
+       status->r = 0;
+
+       struct nlattr *attrs;
+       struct nlattr *tb[NLMSGERR_ATTR_MAX + 1];
+       struct nlmsghdr* nlh = (struct nlmsghdr*)err - 1;
+
+       size_t len = nlh->nlmsg_len;
+       size_t ack_len = sizeof(*nlh) + sizeof(int) + sizeof(*nlh);
+
+       status->r = err->error;
+       if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS))
+               return NL_STOP;
+
+       if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
+               ack_len += err->msg.nlmsg_len - sizeof(*nlh);
+
+       if (len <= ack_len)
+               return NL_STOP;
+
+       attrs = (void *)((unsigned char *)nlh + ack_len);
+       len -= ack_len;
+
+       nla_parse(tb, NLMSGERR_ATTR_MAX, attrs, len, NULL);
+       if (tb[NLMSGERR_ATTR_MSG]) {
+               len = strnlen((char *)nla_data(tb[NLMSGERR_ATTR_MSG]),
+                             nla_len(tb[NLMSGERR_ATTR_MSG]));
+
+               ERROR(status->ctx, "Kernel reports: %*s\n", len,
+                       (const char *)nla_data(tb[NLMSGERR_ATTR_MSG]));
+       }
+
+       return NL_STOP;
+}
+
 // Sends a netlink message and calls the handler to handle the result
 int network_send_netlink_message(struct network_ctx* ctx, struct nl_msg* msg,
                int(*handler)(struct nl_msg* msg, void* data), void* data) {
+       struct network_netlink_message_status status;
+       status.ctx = ctx;
+
        DEBUG(ctx, "Sending netlink message %p\n", msg);
 
        // Sending the message
-       int r = nl_send_auto(ctx->nl_socket, msg);
-       if (r < 0) {
-               ERROR(ctx, "Error sending netlink message: %d\n", r);
-               return r;
+       status.r = nl_send_auto(ctx->nl_socket, msg);
+       if (status.r < 0) {
+               ERROR(ctx, "Error sending netlink message: %d\n", status.r);
+               return status.r;
        }
 
        // Register callback
@@ -249,16 +294,17 @@ int network_send_netlink_message(struct network_ctx* ctx, struct nl_msg* msg,
                return -1;
        }
 
-       r = 1;
+       status.r = 1;
 
        nl_cb_set(callback, NL_CB_VALID, NL_CB_CUSTOM, handler, data);
-       nl_cb_set(callback, NL_CB_ACK, NL_CB_CUSTOM, __nl_ack_handler, &r);
-       nl_cb_set(callback, NL_CB_FINISH, NL_CB_CUSTOM, __nl_finish_handler, &r);
+       nl_cb_set(callback, NL_CB_ACK, NL_CB_CUSTOM, __nl_ack_handler, &status);
+       nl_cb_set(callback, NL_CB_FINISH, NL_CB_CUSTOM, __nl_finish_handler, &status);
+       nl_cb_err(callback, NL_CB_CUSTOM, __nl_error_handler, &status);
 
-       while (r > 0)
+       while (status.r > 0)
                nl_recvmsgs(ctx->nl_socket, callback);
 
-       DEBUG(ctx, "Netlink message returned with status %d\n", r);
+       DEBUG(ctx, "Netlink message returned with status %d\n", status.r);
 
-       return r;
+       return status.r;
 }