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platform: print error message from netlink extended ack

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From v4.12 the kernel appends some attributes to netlink acks
containing a textual description of the error and other fields (see
commit [1]). Parse those attributes and print the error message.

Examples:

platform-linux: netlink: recvmsg: error message from kernel: Network is unreachable (101) "Nexthop has invalid gateway" for request 12

platform-linux: netlink: recvmsg: error message from kernel: Invalid argument (22) "Local address cannot be multicast" for request 21

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2d4bc93368f5a0ddb57c8c885cdad9c9b7a10ed5
This commit is contained in:
Beniamino Galvani
2018-03-08 17:01:35 +01:00
parent 26c215e22d
commit b107e121b0
3 changed files with 56 additions and 2 deletions
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25
src/platform/nm-linux-platform.c
View File

@@ -6596,11 +6596,30 @@ continue_reading:
abort_parsing = TRUE;
} else if (e->error) {
int errsv = e->error > 0 ? e->error : -e->error;
const char *extack_msg = NULL;
if ( NM_FLAGS_HAS (hdr->nlmsg_flags, NLM_F_ACK_TLVS)
&& hdr->nlmsg_len >= sizeof (*e) + e->msg.nlmsg_len) {
static const struct nla_policy policy[NLMSGERR_ATTR_MAX + 1] = {
[NLMSGERR_ATTR_MSG] = { .type = NLA_STRING },
[NLMSGERR_ATTR_OFFS] = { .type = NLA_U32 },
};
struct nlattr *tb[NLMSGERR_ATTR_MAX + 1];
struct nlattr *tlvs;
tlvs = (struct nlattr *) ((char *) e + sizeof (*e) + e->msg.nlmsg_len - NLMSG_HDRLEN);
if (!nla_parse (tb, NLMSGERR_ATTR_MAX, tlvs,
hdr->nlmsg_len - sizeof (*e) - e->msg.nlmsg_len, policy)) {
if (tb[NLMSGERR_ATTR_MSG])
extack_msg = nla_get_string (tb[NLMSGERR_ATTR_MSG]);
}
}
/* Error message reported back from kernel. */
_LOGD ("netlink: recvmsg: error message from kernel: %s (%d) for request %d",
_LOGD ("netlink: recvmsg: error message from kernel: %s (%d)%s%s%s for request %d",
strerror (errsv),
errsv,
NM_PRINT_FMT_QUOTED (extack_msg, " \"", extack_msg, "\"", ""),
nlmsg_hdr (msg)->nlmsg_seq);
seq_result = -errsv;
} else
@@ -6948,6 +6967,10 @@ constructed (GObject *_object)
nle = nl_socket_set_buffer_size (priv->nlh, 8*1024*1024, 0);
g_assert (!nle);
nle = nl_socket_set_ext_ack (priv->nlh, TRUE);
if (nle)
_LOGD ("could not enable extended acks on netlink socket");
/* explicitly set the msg buffer size and disable MSG_PEEK.
* If we later encounter NLE_MSG_TRUNC, we will adjust the buffer size. */
nl_socket_disable_msg_peek (priv->nlh);