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tcpconns plugin: Only chose between netlink / proc on the first itera…

…tion.

Rather than going for netlink each iteration and fall back to /proc, try
this on the first iteration only and stick with the result afterwards.
Also contains some improvements to the error handling / reporting.
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1 parent 44f3746 commit f52ebcb1bc8e170909078eb3eb2e3d103e4ca9d2 @octo committed Aug 27, 2012
Showing with 98 additions and 39 deletions.
  1. +98 −39 src/tcpconns.c
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137 src/tcpconns.c
@@ -275,6 +275,17 @@ static int config_keys_num = STATIC_ARRAY_SIZE (config_keys);
static int port_collect_listening = 0;
static port_entry_t *port_list_head = NULL;
+static uint32_t sequence_number = 0;
+
+#if KERNEL_LINUX
+enum
+{
+ SRC_DUNNO,
+ SRC_NETLINK,
+ SRC_PROC
+} linux_source = SRC_DUNNO;
+#endif
+
static void conn_submit_port_entry (port_entry_t *pe)
{
value_t values[1];
@@ -431,6 +442,8 @@ static int conn_handle_ports (uint16_t port_local, uint16_t port_remote, uint8_t
} /* int conn_handle_ports */
#if KERNEL_LINUX
+/* Returns zero on success, less than zero on socket error and greater than
+ * zero on other errors. */
static int conn_read_netlink (void)
{
int fd;
@@ -440,11 +453,17 @@ static int conn_read_netlink (void)
struct iovec iov;
struct inet_diag_msg *r;
char buf[8192];
- static uint32_t sequence_number = 0;
+ /* If this fails, it's likely a permission problem. We'll fall back to
+ * reading this information from files below. */
fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_INET_DIAG);
if (fd < 0)
- return (1);
+ {
+ ERROR ("tcpconns plugin: conn_read_netlink: socket(AF_NETLINK, SOCK_RAW, "
+ "NETLINK_INET_DIAG) failed: %s",
+ sstrerror (errno, buf, sizeof (buf)));
+ return (-1);
+ }
memset(&nladdr, 0, sizeof(nladdr));
nladdr.nl_family = AF_NETLINK;
@@ -477,8 +496,10 @@ static int conn_read_netlink (void)
if (sendmsg (fd, &msg, 0) < 0)
{
+ ERROR ("tcpconns plugin: conn_read_netlink: sendmsg(2) failed: %s",
+ sstrerror (errno, buf, sizeof (buf)));
close (fd);
- return (1);
+ return (-1);
}
iov.iov_base = buf;
@@ -498,44 +519,58 @@ static int conn_read_netlink (void)
status = recvmsg(fd, (void *) &msg, /* flags = */ 0);
if (status < 0)
{
- if (errno == EINTR)
+ if ((errno == EINTR) || (errno == EAGAIN))
continue;
+
+ ERROR ("tcpconns plugin: conn_read_netlink: recvmsg(2) failed: %s",
+ sstrerror (errno, buf, sizeof (buf)));
close (fd);
- return (1);
+ return (-1);
}
-
- if (status == 0)
+ else if (status == 0)
{
close (fd);
+ DEBUG ("tcpconns plugin: conn_read_netlink: Unexpected zero-sized "
+ "reply from netlink socket.");
return (0);
}
h = (struct nlmsghdr*)buf;
while (NLMSG_OK(h, status))
{
- if (h->nlmsg_seq == sequence_number)
+ if (h->nlmsg_seq != sequence_number)
{
- if (h->nlmsg_type == NLMSG_DONE)
- {
- close (fd);
- return (0);
- }
- else if (h->nlmsg_type == NLMSG_ERROR)
- {
- close (fd);
- return (1);
- }
-
- r = NLMSG_DATA(h);
-
- /* This code does not (need to) distinguish between IPv4 and IPv6. */
- conn_handle_ports (ntohs(r->id.idiag_sport),
- ntohs(r->id.idiag_dport),
- r->idiag_state);
+ h = NLMSG_NEXT(h, status);
+ continue;
}
+
+ if (h->nlmsg_type == NLMSG_DONE)
+ {
+ close (fd);
+ return (0);
+ }
+ else if (h->nlmsg_type == NLMSG_ERROR)
+ {
+ struct nlmsgerr *msg_error;
+
+ msg_error = NLMSG_DATA(h);
+ WARNING ("tcpconns plugin: conn_read_netlink: Received error %i.",
+ msg_error->error);
+
+ close (fd);
+ return (1);
+ }
+
+ r = NLMSG_DATA(h);
+
+ /* This code does not (need to) distinguish between IPv4 and IPv6. */
+ conn_handle_ports (ntohs(r->id.idiag_sport),
+ ntohs(r->id.idiag_dport),
+ r->idiag_state);
+
h = NLMSG_NEXT(h, status);
- }
- }
+ } /* while (NLMSG_OK) */
+ } /* while (1) */
/* Not reached because the while() loop above handles the exit condition. */
return (0);
@@ -675,31 +710,55 @@ static int conn_init (void)
static int conn_read (void)
{
- int errors_num = 0;
+ int status;
conn_reset_port_entry ();
- /* Try to use netlink for getting this data, it is _much_ faster on systems
- * with a large amount of connections. */
- if (conn_read_netlink () != 0)
+ if (linux_source == SRC_NETLINK)
{
+ status = conn_read_netlink ();
+ }
+ else if (linux_source == SRC_PROC)
+ {
+ int errors_num = 0;
+
if (conn_read_file ("/proc/net/tcp") != 0)
errors_num++;
if (conn_read_file ("/proc/net/tcp6") != 0)
errors_num++;
- }
- if (errors_num < 2)
- {
- conn_submit_all ();
+ if (errors_num < 2)
+ status = 0;
+ else
+ status = ENOENT;
}
- else
+ else /* if (linux_source == SRC_DUNNO) */
{
- ERROR ("tcpconns plugin: Neither /proc/net/tcp nor /proc/net/tcp6 "
- "could be read.");
- return (-1);
+ /* Try to use netlink for getting this data, it is _much_ faster on systems
+ * with a large amount of connections. */
+ status = conn_read_netlink ();
+ if (status == 0)
+ {
+ INFO ("tcpconns plugin: Reading from netlink succeeded. "
+ "Will use the netlink method from now on.");
+ linux_source = SRC_NETLINK;
+ }
+ else
+ {
+ INFO ("tcpconns plugin: Reading from netlink failed. "
+ "Will read from /proc from now on.");
+ linux_source = SRC_PROC;
+
+ /* return success here to avoid the "plugin failed" message. */
+ return (0);
+ }
}
+ if (status == 0)
+ conn_submit_all ();
+ else
+ return (status);
+
return (0);
} /* int conn_read */
/* #endif KERNEL_LINUX */

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