diff -urNp old/include/net-snmp/library/large_fd_set.h new/include/net-snmp/library/large_fd_set.h

--- old/include/net-snmp/library/large_fd_set.h	2012-10-10 00:28:58.000000000 +0200

+++ new/include/net-snmp/library/large_fd_set.h	2017-04-04 14:36:27.307180033 +0200

@@ -55,8 +55,9 @@ extern "C" {

  * Number of bytes needed to store a number of file descriptors as a

  * struct fd_set.

  */

-#define NETSNMP_FD_SET_BYTES(setsize)                           \

-    (sizeof(fd_set) + ((setsize) - FD_SETSIZE) * sizeof(SOCKET))

+#define NETSNMP_FD_SET_BYTES(setsize)                                   \

+    (sizeof(fd_set) + ((setsize) > FD_SETSIZE ?                         \

+                       ((setsize) - FD_SETSIZE) * sizeof(SOCKET) : 0))

 /** Remove all sockets from the set *fdset. */

 #define NETSNMP_LARGE_FD_ZERO(fdset) \

@@ -91,9 +92,10 @@ int    netsnmp_large_fd_is_set(SOCKET fd

  * Number of bytes needed to store a number of file descriptors as a

  * struct fd_set.

  */

-#define NETSNMP_FD_SET_BYTES(setsize)                                   \

-    (sizeof(fd_set) + NETSNMP_FD_SET_ELEM_COUNT((setsize) - FD_SETSIZE) \

-     * NETSNMP_FD_MASK_SIZE)

+#define NETSNMP_FD_SET_BYTES(setsize)                                    \

+    (sizeof(fd_set) + ((setsize) > FD_SETSIZE ?                          \

+                       NETSNMP_FD_SET_ELEM_COUNT((setsize) - FD_SETSIZE) \

+                       * NETSNMP_FD_MASK_SIZE : 0))

 /** Remove all file descriptors from the set *fdset. */

 #define NETSNMP_LARGE_FD_ZERO(fdset)                            \

diff -urNp old/snmplib/large_fd_set.c new/snmplib/large_fd_set.c

--- old/snmplib/large_fd_set.c	2012-10-10 00:28:58.000000000 +0200

+++ new/snmplib/large_fd_set.c	2017-04-04 15:03:20.580810774 +0200

@@ -21,6 +21,10 @@

 #if !defined(cygwin) && defined(HAVE_WINSOCK_H)

+#define LFD_SET(n, p)    FD_SET(n, p)

+#define LFD_CLR(n, p)    FD_CLR(n, p)

+#define LFD_ISSET(n, p)  FD_ISSET(n, p)

+

 void

 netsnmp_large_fd_setfd(SOCKET fd, netsnmp_large_fd_set * fdset)

 {

@@ -28,18 +32,18 @@ netsnmp_large_fd_setfd(SOCKET fd, netsnm

     netsnmp_assert(fd != INVALID_SOCKET);

-    if (fdset->lfs_set.fd_count == fdset->lfs_setsize)

+    if (fdset->lfs_setptr->fd_count == fdset->lfs_setsize)

         netsnmp_large_fd_set_resize(fdset, 2 * (fdset->lfs_setsize + 1));

-    for (i = 0; i < fdset->lfs_set.fd_count; i++) {

-        if (fdset->lfs_set.fd_array[i] == (SOCKET) (fd))

+    for (i = 0; i < fdset->lfs_setptr->fd_count; i++) {

+        if (fdset->lfs_setptr->fd_array[i] == fd)

             break;

     }

-    if (i == fdset->lfs_set.fd_count

-        && fdset->lfs_set.fd_count < fdset->lfs_setsize) {

-        fdset->lfs_set.fd_count++;

-        fdset->lfs_set.fd_array[i] = fd;

+    if (i == fdset->lfs_setptr->fd_count &&

+        fdset->lfs_setptr->fd_count < fdset->lfs_setsize) {

+        fdset->lfs_setptr->fd_count++;

+        fdset->lfs_setptr->fd_array[i] = fd;

     }

 }

@@ -50,14 +54,14 @@ netsnmp_large_fd_clr(SOCKET fd, netsnmp_

     netsnmp_assert(fd != INVALID_SOCKET);

-    for (i = 0; i < fdset->lfs_set.fd_count; i++) {

-        if (fdset->lfs_set.fd_array[i] == fd) {

-            while (i < fdset->lfs_set.fd_count - 1) {

-                fdset->lfs_set.fd_array[i] =

-                    fdset->lfs_set.fd_array[i + 1];

+    for (i = 0; i < fdset->lfs_setptr->fd_count; i++) {

+        if (fdset->lfs_setptr->fd_array[i] == fd) {

+            while (i < fdset->lfs_setptr->fd_count - 1) {

+                fdset->lfs_setptr->fd_array[i] =

+                    fdset->lfs_setptr->fd_array[i + 1];

                 i++;

             }

-            fdset->lfs_set.fd_count--;

+            fdset->lfs_setptr->fd_count--;

             break;

         }

     }

@@ -70,8 +74,8 @@ netsnmp_large_fd_is_set(SOCKET fd, netsn

     netsnmp_assert(fd != INVALID_SOCKET);

-    for (i = 0; i < fdset->lfs_set.fd_count; i++) {

-        if (fdset->lfs_set.fd_array[i] == fd)

+    for (i = 0; i < fdset->lfs_setptr->fd_count; i++) {

+        if (fdset->lfs_setptr->fd_array[i] == fd)

             return 1;

     }

     return 0;

@@ -79,6 +83,43 @@ netsnmp_large_fd_is_set(SOCKET fd, netsn

 #else

+ /*

+ * Recent versions of glibc trigger abort() if FD_SET(), FD_CLR() or

+ * FD_ISSET() is invoked with n >= FD_SETSIZE. Hence these replacement

+ * functions. However, since NFDBITS != 8 * sizeof(fd_set.fds_bits[0]) for at

+ * least HP-UX on ia64 and since that combination uses big endian, use the

+ * macros from <sys/select.h> on such systems.

+ */

+NETSNMP_STATIC_INLINE void LFD_SET(unsigned n, fd_set *p)

+{

+    enum { nfdbits = 8 * sizeof(p->fds_bits[0]) };

+

+    if (nfdbits == NFDBITS)

+        p->fds_bits[n / nfdbits] |= (1ULL << (n % nfdbits));

+    else

+        FD_SET(n, p);

+}

+

+NETSNMP_STATIC_INLINE void LFD_CLR(unsigned n, fd_set *p)

+{

+    enum { nfdbits = 8 * sizeof(p->fds_bits[0]) };

+

+    if (nfdbits == NFDBITS)

+        p->fds_bits[n / nfdbits] &= ~(1ULL << (n % nfdbits));

+    else

+        FD_CLR(n, p);

+}

+

+NETSNMP_STATIC_INLINE unsigned LFD_ISSET(unsigned n, const fd_set *p)

+{

+    enum { nfdbits = 8 * sizeof(p->fds_bits[0]) };

+

+    if (nfdbits == NFDBITS)

+        return (p->fds_bits[n / nfdbits] & (1ULL << (n % nfdbits))) != 0;

+    else

+        return FD_ISSET(n, p) != 0;

+}

+

 void

 netsnmp_large_fd_setfd(int fd, netsnmp_large_fd_set * fdset)

 {

@@ -87,7 +128,7 @@ netsnmp_large_fd_setfd(int fd, netsnmp_l

     while (fd >= (int)fdset->lfs_setsize)

         netsnmp_large_fd_set_resize(fdset, 2 * (fdset->lfs_setsize + 1));

-    FD_SET(fd, fdset->lfs_setptr);

+    LFD_SET(fd, fdset->lfs_setptr);

 }

 void

@@ -96,7 +137,7 @@ netsnmp_large_fd_clr(int fd, netsnmp_lar

     netsnmp_assert(fd >= 0);

     if ((unsigned)fd < fdset->lfs_setsize)

-        FD_CLR(fd, fdset->lfs_setptr);

+        LFD_CLR(fd, fdset->lfs_setptr);

 }

 int

@@ -104,7 +145,7 @@ netsnmp_large_fd_is_set(int fd, netsnmp_

 {

     netsnmp_assert(fd >= 0);

-    return (unsigned)fd < fdset->lfs_setsize && FD_ISSET(fd, fdset->lfs_setptr);

+    return ((unsigned)fd < fdset->lfs_setsize && LFD_ISSET(fd, fdset->lfs_setptr));

 }

 #endif

@@ -174,22 +215,24 @@ netsnmp_large_fd_set_resize(netsnmp_larg

     }

 #if defined(cygwin) || !defined(HAVE_WINSOCK_H)

-    {

+    /*

+     * Unix: when enlarging, clear the file descriptors defined in the

+     * resized *fdset but that were not defined in the original *fdset.

+     */

+    if ( fdset->lfs_setsize == 0 && setsize == FD_SETSIZE ) {

+        /* In this case we can use the OS's FD_ZERO */

+        FD_ZERO(fdset->lfs_setptr);

+    } else {

         int             i;

-

-        /*

-         * Unix: when enlarging, clear the file descriptors defined in the

-         * resized *fdset but that were not defined in the original *fdset.

-         */

         for (i = fdset->lfs_setsize; i < setsize; i++)

-            FD_CLR(i, fdset->lfs_setptr);

+            LFD_CLR(i, fdset->lfs_setptr);

     }

 #endif

     fdset->lfs_setsize = setsize;

 #if !defined(cygwin) && defined(HAVE_WINSOCK_H)

-    if (setsize < fdset->lfs_set.fd_count)

-        fdset->lfs_set.fd_count = setsize;

+    if (setsize < fdset->lfs_setptr->fd_count)

+        fdset->lfs_setptr->fd_count = setsize;

 #endif

 success:

     return 1;

@@ -197,7 +240,7 @@ success:

 out_of_mem:

     fdset->lfs_setsize = 0;

 #if !defined(cygwin) && defined(HAVE_WINSOCK_H)

-    fdset->lfs_set.fd_count = 0;

+    fdset->lfs_setptr->fd_count = 0;

 #endif

     return 0;

 }