svn commit: r359922 - head/sys/kern

[Jonathan T. Looney]

Author: jtl
Date: Tue Apr 14 15:30:34 2020
New Revision: 359922
URL: https://svnweb.freebsd.org/changeset/base/359922

Log:
  Print more detail as part of the sonewconn() overflow message.
  
  When a socket's listen queue overflows, sonewconn() emits a debug-level
  log message. These messages are sometimes useful to systems administrators
  in highlighting a process which is not keeping up with its listen queue.
  
  This commit attempts to enhance the usefulness of this message by printing
  more details about the socket's address. If all else fails, it will at
  least print the domain name of the socket.
  
  Reviewed by:	bz, jhb, kbowling
  MFC after:	2 weeks
  Sponsored by:	Netflix, Inc.
  Differential Revision:	https://reviews.freebsd.org/D24272

Modified:
  head/sys/kern/uipc_socket.c

Modified: head/sys/kern/uipc_socket.c
==============================================================================
--- head/sys/kern/uipc_socket.c	Tue Apr 14 15:27:24 2020	(r359921)
+++ head/sys/kern/uipc_socket.c	Tue Apr 14 15:30:34 2020	(r359922)
@@ -130,6 +130,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/poll.h>
 #include <sys/proc.h>
 #include <sys/protosw.h>
+#include <sys/sbuf.h>
 #include <sys/socket.h>
 #include <sys/socketvar.h>
 #include <sys/resourcevar.h>
@@ -140,9 +141,12 @@ __FBSDID("$FreeBSD$");
 #include <sys/sysctl.h>
 #include <sys/taskqueue.h>
 #include <sys/uio.h>
+#include <sys/un.h>
+#include <sys/unpcb.h>
 #include <sys/jail.h>
 #include <sys/syslog.h>
 #include <netinet/in.h>
+#include <netinet/in_pcb.h>
 #include <netinet/tcp.h>
 
 #include <net/vnet.h>
@@ -587,8 +591,17 @@ sonewconn(struct socket *head, int connstatus)
 	static struct timeval overinterval = { 60, 0 };
 	static int overcount;
 
+	struct sbuf descrsb;
 	struct socket *so;
 	u_int over;
+	int len;
+	const char localprefix[] = "local:";
+	char descrbuf[SUNPATHLEN + sizeof(localprefix)];
+#if defined(INET6)
+	char addrbuf[INET6_ADDRSTRLEN];
+#elif defined(INET)
+	char addrbuf[INET_ADDRSTRLEN];
+#endif
 
 	SOLISTEN_LOCK(head);
 	over = (head->sol_qlen > 3 * head->sol_qlimit / 2);
@@ -601,10 +614,80 @@ sonewconn(struct socket *head, int connstatus)
 		overcount++;
 
 		if (ratecheck(&lastover, &overinterval)) {
-			log(LOG_DEBUG, "%s: pcb %p: Listen queue overflow: "
+			/*
+			 * Try to print something descriptive about the
+			 * socket for the error message.
+			 */
+			sbuf_new(&descrsb, descrbuf, sizeof(descrbuf),
+			    SBUF_FIXEDLEN);
+			switch (head->so_proto->pr_domain->dom_family) {
+#if defined(INET) || defined(INET6)
+#ifdef INET
+			case AF_INET:
+#endif
+#ifdef INET6
+			case AF_INET6:
+				if (head->so_proto->pr_domain->dom_family ==
+				    AF_INET6 ||
+				    (sotoinpcb(head)->inp_inc.inc_flags &
+				    INC_ISIPV6)) {
+					ip6_sprintf(addrbuf,
+					    &sotoinpcb(head)->inp_inc.inc6_laddr);
+					sbuf_printf(&descrsb, "[%s]", addrbuf);
+				} else
+#endif
+				{
+#ifdef INET
+					inet_ntoa_r(
+					    sotoinpcb(head)->inp_inc.inc_laddr,
+					    addrbuf);
+					sbuf_cat(&descrsb, addrbuf);
+#endif
+				}
+				sbuf_printf(&descrsb, ":%hu (proto %u)",
+				    ntohs(sotoinpcb(head)->inp_inc.inc_lport),
+				    head->so_proto->pr_protocol);
+				break;
+#endif /* INET || INET6 */
+			case AF_UNIX:
+				sbuf_cat(&descrsb, localprefix);
+				if (sotounpcb(head)->unp_addr != NULL)
+					len =
+					    sotounpcb(head)->unp_addr->sun_len -
+					    offsetof(struct sockaddr_un,
+					    sun_path);
+				else
+					len = 0;
+				if (len > 0)
+					sbuf_bcat(&descrsb,
+					    sotounpcb(head)->unp_addr->sun_path,
+					    len);
+				else
+					sbuf_cat(&descrsb, "(unknown)");
+				break;
+			}
+
+			/*
+			 * If we can't print something more specific, at least
+			 * print the domain name.
+			 */
+			if (sbuf_finish(&descrsb) != 0 ||
+			    sbuf_len(&descrsb) <= 0) {
+				sbuf_clear(&descrsb);
+				sbuf_cat(&descrsb,
+				    head->so_proto->pr_domain->dom_name ?:
+				    "unknown");
+				sbuf_finish(&descrsb);
+			}
+			KASSERT(sbuf_len(&descrsb) > 0,
+			    ("%s: sbuf creation failed", __func__));
+			log(LOG_DEBUG,
+			    "%s: pcb %p (%s): Listen queue overflow: "
 			    "%i already in queue awaiting acceptance "
 			    "(%d occurrences)\n",
-			    __func__, head->so_pcb, head->sol_qlen, overcount);
+			    __func__, head->so_pcb, sbuf_data(&descrsb),
+			    head->sol_qlen, overcount);
+			sbuf_delete(&descrsb);
 
 			overcount = 0;
 		}