File kdump-avoid-endless-loop-EAI_AGAIN.patch of Package kdump.21349

Date: Thu Mar 25 12:48:54 2021 +0100
From: Petr Pavlu <petr.pavlu@suse.com>
Subject: Avoid an endless loop when resolving a hostname fails with EAI_AGAIN
References: bsc#1183070
Upstream: merged
Git-commit: 716883423f45acf3271c200353dce074d6ffc5be

Method Routable::resolve() invokes function getaddrinfo() to obtain a
network address for a given hostname. This operation can fail with the
error code EAI_AGAIN to indicate that the name server encountered a
temporary failure. Routable::resolve() reacts to this situation by
calling getaddrinfo() again which can result in an endless loop if the
function continues to return this error code. It is not guaranteed that
the underlying reason for EAI_AGAIN will go away in some bounded time.

The patch removes the EAI_AGAIN loop in Routable::resolve() and updates
the retry code in Routable::check() to repeatedly attempt resolving a
hostname until it succeeds or a specified timeout for network operations
is reached.

---
 kdumptool/routable.cc |   38 ++++++++++++++++++++++++++++++--------
 1 file changed, 30 insertions(+), 8 deletions(-)

--- a/kdumptool/routable.cc
+++ b/kdumptool/routable.cc
@@ -17,6 +17,7 @@
  * 02110-1301, USA.
  */
 
+#include <algorithm>
 #include <string.h>
 
 #include <unistd.h>
@@ -36,6 +37,8 @@
 #include "stringutil.h"
 #include "debug.h"
 
+using std::min;
+
 //{{{ NetLink ------------------------------------------------------------------
 
 #define NETLINK_DEF_RECV_MAX	1024
@@ -475,9 +478,7 @@ bool Routable::resolve(void)
     memset(&hints, 0, sizeof hints);
     hints.ai_family = AF_UNSPEC;
     hints.ai_socktype = SOCK_RAW;
-    do {
-	res = getaddrinfo(raw_host.c_str(), NULL, &hints, &m_ai);
-    } while (res == EAI_AGAIN);
+    res = getaddrinfo(raw_host.c_str(), NULL, &hints, &m_ai);
 
     if (res == 0)
 	return true;
@@ -485,7 +486,8 @@ bool Routable::resolve(void)
     if (res == EAI_SYSTEM)
 	throw KSystemError("Name resolution failed", errno);
 
-    if (res != EAI_NONAME && res != EAI_FAIL && res != EAI_NODATA)
+    if (res != EAI_NONAME && res != EAI_FAIL && res != EAI_NODATA &&
+        res != EAI_AGAIN)
 	throw KGaiError("Name resolution failed", res);
 
     return false;
@@ -494,13 +496,33 @@ bool Routable::resolve(void)
 // -----------------------------------------------------------------------------
 bool Routable::check(int timeout)
 {
+    // Resolve the target hostname. An attempt is made regularly until the
+    // hostname can be resolved or a specified timeout for network operations
+    // is reached.
+    struct timespec tstop;
+    clock_gettime(CLOCK_MONOTONIC, &tstop);
+    tstop.tv_sec += timeout;
+
+    while (!resolve()) {
+        struct timespec tsnow;
+        clock_gettime(CLOCK_MONOTONIC, &tsnow);
+        int interval = (tstop.tv_sec - tsnow.tv_sec) * 1000;
+        interval += (tstop.tv_nsec - tsnow.tv_nsec) / 1000000L;
+        if (interval <= 0)
+            return false;
+
+        // Sleep, at most for 1 second.
+        struct timespec wait_period;
+        interval = min(interval, 1000);
+        wait_period.tv_sec = interval / 1000;
+        wait_period.tv_nsec = (interval % 1000) * 1000 * 1000;
+        nanosleep(&wait_period, NULL);
+    }
+
+    // Check there is an existing route.
     NetLink nl(RTMGRP_IPV4_ROUTE | RTMGRP_IPV6_ROUTE);
     nl.setTimeout(timeout);
 
-    while (!resolve())
-	if (nl.waitRouteChange() != 0)
-	    return false;
-
     while (!hasRoute())
 	if (nl.waitRouteChange() != 0)
 	    return false;