kernel: Make range of SPIs for IPsec SAs configurable

conf/options/charon.opt

@@ -350,6 +350,12 @@ charon.signature_authentication_constraints = yes
 	certificate chain, are also used as constraints against the signature scheme
 	used by peers during IKEv2.
 
+charon.spi_min = 0xc0000000
+	The lower limit for SPIs requested from the kernel for IPsec SAs.
+
+charon.spi_max = 0xcfffffff
+	The upper limit for SPIs requested from the kernel for IPsec SAs.
+
 charon.start-scripts {}
 	Section containing a list of scripts (name = path) that are executed when
 	the daemon is started.

src/libcharon/kernel/kernel_interface.h

@@ -56,6 +56,12 @@ typedef enum kernel_feature_t kernel_feature_t;
 #include <kernel/kernel_ipsec.h>
 #include <kernel/kernel_net.h>
 
+/**
+ * Default range for SPIs requested from kernels
+ */
+#define KERNEL_SPI_MIN 0xc0000000
+#define KERNEL_SPI_MAX 0xcfffffff
+
 /**
  * Bitfield of optional features a kernel backend supports.
  *

src/libcharon/plugins/kernel_netlink/kernel_netlink_ipsec.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2006-2016 Tobias Brunner
+ * Copyright (C) 2006-2017 Tobias Brunner
  * Copyright (C) 2005-2009 Martin Willi
  * Copyright (C) 2008-2016 Andreas Steffen
  * Copyright (C) 2006-2007 Fabian Hartmann, Noah Heusser
@@ -1211,8 +1211,15 @@ METHOD(kernel_ipsec_t, get_spi, status_t,
 	private_kernel_netlink_ipsec_t *this, host_t *src, host_t *dst,
 	uint8_t protocol, uint32_t *spi)
 {
-	if (get_spi_internal(this, src, dst, protocol,
+	uint32_t spi_min, spi_max;
-						 0xc0000000, 0xcFFFFFFF, spi) != SUCCESS)
+
+	spi_min = lib->settings->get_int(lib->settings, "%s.spi_min",
+									 KERNEL_SPI_MIN, lib->ns);
+	spi_max = lib->settings->get_int(lib->settings, "%s.spi_max",
+									 KERNEL_SPI_MAX, lib->ns);
+
+	if (get_spi_internal(this, src, dst, protocol, min(spi_min, spi_max),
+						 max(spi_min, spi_max), spi) != SUCCESS)
 	{
 		DBG1(DBG_KNL, "unable to get SPI");
 		return FAILED;

src/libcharon/plugins/kernel_pfkey/kernel_pfkey_ipsec.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008-2016 Tobias Brunner
+ * Copyright (C) 2008-2017 Tobias Brunner
  * Copyright (C) 2008 Andreas Steffen
  * HSR Hochschule fuer Technik Rapperswil
  *
@@ -1586,8 +1586,15 @@ METHOD(kernel_ipsec_t, get_spi, status_t,
 	private_kernel_pfkey_ipsec_t *this, host_t *src, host_t *dst,
 	uint8_t protocol, uint32_t *spi)
 {
-	if (get_spi_internal(this, src, dst, protocol,
+	uint32_t spi_min, spi_max;
-						 0xc0000000, 0xcFFFFFFF, spi) != SUCCESS)
+
+	spi_min = lib->settings->get_int(lib->settings, "%s.spi_min",
+									 KERNEL_SPI_MIN, lib->ns);
+	spi_max = lib->settings->get_int(lib->settings, "%s.spi_max",
+									 KERNEL_SPI_MAX, lib->ns);
+
+	if (get_spi_internal(this, src, dst, protocol, min(spi_min, spi_max),
+						 max(spi_min, spi_max), spi) != SUCCESS)
 	{
 		DBG1(DBG_KNL, "unable to get SPI");
 		return FAILED;

src/libipsec/ipsec_sa_mgr.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2012 Tobias Brunner
+ * Copyright (C) 2012-2017 Tobias Brunner
  * Copyright (C) 2012 Giuliano Grassi
  * Copyright (C) 2012 Ralf Sager
  * Hochschule fuer Technik Rapperswil
@@ -398,7 +398,18 @@ METHOD(ipsec_sa_mgr_t, get_spi, status_t,
 	private_ipsec_sa_mgr_t *this, host_t *src, host_t *dst, uint8_t protocol,
 	uint32_t *spi)
 {
-	uint32_t spi_new;
+	uint32_t spi_min, spi_max, spi_new;
+
+	spi_min = lib->settings->get_int(lib->settings, "%s.spi_min",
+									 KERNEL_SPI_MIN, lib->ns);
+	spi_max = lib->settings->get_int(lib->settings, "%s.spi_max",
+									 KERNEL_SPI_MAX, lib->ns);
+	if (spi_min > spi_max)
+	{
+		spi_new = spi_min;
+		spi_min = spi_max;
+		spi_max = spi_new;
+	}
 
 	this->mutex->lock(this->mutex);
 	if (!this->rng)
@@ -421,6 +432,7 @@ METHOD(ipsec_sa_mgr_t, get_spi, status_t,
 			DBG1(DBG_ESP, "failed to allocate SPI");
 			return FAILED;
 		}
+		spi_new = spi_min + spi_new % (spi_max - spi_min + 1);
 		/* make sure the SPI is valid (not in range 0-255) */
 		spi_new |= 0x00000100;
 		spi_new = htonl(spi_new);