[PATCH iproute2-next 0/2] GTP support for ip link and tc flower

[PATCH iproute2-next 0/2] GTP support for ip link and tc flower

[Wojciech Drewek]

This patch series introduces GTP support to iproute2. Since this patch
series it is possible to create net devices of GTP type. Then, those
devices can be used in tc in order to offload GTP packets. New field
in tc flower (gtp_opts) can be used to match on QFI and PDU type.

Kernel changes:
https://lore.kernel.org/netdev/20220127125525.125805-1-marcin.szycik@linux.intel.com/T/#u

Wojciech Drewek (2):
  ip: GTP support in ip link
  f_flower: Implement gtp options support

 include/uapi/linux/pkt_cls.h |  16 +++++
 ip/Makefile                  |   2 +-
 ip/iplink.c                  |   2 +-
 ip/iplink_gtp.c              | 116 +++++++++++++++++++++++++++++++++
 man/man8/ip-link.8.in        |  25 +++++++-
 man/man8/tc-flower.8         |  10 +++
 tc/f_flower.c                | 120 +++++++++++++++++++++++++++++++++++
 7 files changed, 288 insertions(+), 3 deletions(-)
 create mode 100644 ip/iplink_gtp.c

-- 
2.31.1

[PATCH iproute2-next 1/2] ip: GTP support in ip link

[Wojciech Drewek]

Support for creating GTP devices through ip link. Two arguments
can be specified by the user when adding device of the GTP type.
 - role (sgsn or ggsn) - indicates whether we are on the GGSN or SGSN
 - hsize - indicates the size of the hash table where PDP sessions
   are stored

IFLA_GTP_FD0 and IFLA_GTP_FD1 arguments would not be provided. Those
are file descriptores to the sockets created in the userspace. Since
we are not going to create sockets in ip link, we don't have to
provide them.

Signed-off-by: Wojciech Drewek <wojciech.drewek@intel.com>
---
 ip/Makefile           |   2 +-
 ip/iplink.c           |   2 +-
 ip/iplink_gtp.c       | 116 ++++++++++++++++++++++++++++++++++++++++++
 man/man8/ip-link.8.in |  25 ++++++++-
 4 files changed, 142 insertions(+), 3 deletions(-)
 create mode 100644 ip/iplink_gtp.c

diff --git a/ip/Makefile b/ip/Makefile
index 2a7a51c313c6..06ba60b341af 100644
--- a/ip/Makefile
+++ b/ip/Makefile
@@ -12,7 +12,7 @@ IPOBJ=ip.o ipaddress.o ipaddrlabel.o iproute.o iprule.o ipnetns.o \
     iplink_geneve.o iplink_vrf.o iproute_lwtunnel.o ipmacsec.o ipila.o \
     ipvrf.o iplink_xstats.o ipseg6.o iplink_netdevsim.o iplink_rmnet.o \
     ipnexthop.o ipmptcp.o iplink_bareudp.o iplink_wwan.o ipioam6.o \
-    iplink_amt.o
+    iplink_amt.o iplink_gtp.o
 
 RTMONOBJ=rtmon.o
 
diff --git a/ip/iplink.c b/ip/iplink.c
index a3ea775d2b23..3d1127f437e4 100644
--- a/ip/iplink.c
+++ b/ip/iplink.c
@@ -57,7 +57,7 @@ void iplink_types_usage(void)
 		"          macsec | macvlan | macvtap |\n"
 		"          netdevsim | nlmon | rmnet | sit | team | team_slave |\n"
 		"          vcan | veth | vlan | vrf | vti | vxcan | vxlan | wwan |\n"
-		"          xfrm }\n");
+		"          xfrm | gtp }\n");
 }
 
 void iplink_usage(void)
diff --git a/ip/iplink_gtp.c b/ip/iplink_gtp.c
new file mode 100644
index 000000000000..d007b45d2c68
--- /dev/null
+++ b/ip/iplink_gtp.c
@@ -0,0 +1,116 @@
+/*
+ * iplink_gtp.c	GTP device support
+ *
+ *		This program is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ *
+ * Authors:	Wojciech Drewek <wojciech.drewek@intel.com>
+ */
+
+#include <stdio.h>
+
+#include "rt_names.h"
+#include "utils.h"
+#include "ip_common.h"
+
+#define GTP_ATTRSET(attrs, type) (((attrs) & (1L << (type))) != 0)
+
+static void print_explain(FILE *f)
+{
+	fprintf(f,
+		"Usage: ... gtp role ROLE\n"
+		"		[ hsize HSIZE ]\n"
+		"\n"
+		"Where:	ROLE   := { sgsn | ggsn }\n"
+		"	HSIZE  := 1-131071\n"
+	);
+}
+
+static void check_duparg(__u32 *attrs, int type, const char *key,
+			 const char *argv)
+{
+	if (!GTP_ATTRSET(*attrs, type)) {
+		*attrs |= (1L << type);
+		return;
+	}
+	duparg2(key, argv);
+}
+
+static int gtp_parse_opt(struct link_util *lu, int argc, char **argv,
+			 struct nlmsghdr *n)
+{
+	__u32 attrs = 0;
+
+	while (argc > 0) {
+		if (!matches(*argv, "role")) {
+			NEXT_ARG();
+			check_duparg(&attrs, IFLA_GTP_ROLE, "role", *argv);
+			if (!strcmp(*argv, "sgsn"))
+				addattr32(n, 1024, IFLA_GTP_ROLE, GTP_ROLE_SGSN);
+			else if (!strcmp(*argv, "ggsn"))
+				addattr32(n, 1024, IFLA_GTP_ROLE, GTP_ROLE_GGSN);
+			else
+				invarg("invalid role, use sgsn or ggsn", *argv);
+		} else if (!matches(*argv, "hsize")) {
+			__u32 hsize;
+
+			NEXT_ARG();
+			check_duparg(&attrs, IFLA_GTP_PDP_HASHSIZE, "hsize", *argv);
+
+			if (get_u32(&hsize, *argv, 0))
+				invarg("invalid PDP hash size", *argv);
+			if (hsize >= 1u << 17)
+				invarg("PDP hash size too big", *argv);
+			addattr32(n, 1024, IFLA_GTP_PDP_HASHSIZE, hsize);
+		} else if (!matches(*argv, "help")) {
+			print_explain(stderr);
+			return -1;
+		}
+		argc--, argv++;
+	}
+
+	if (!GTP_ATTRSET(attrs, IFLA_GTP_ROLE)) {
+		fprintf(stderr, "gtp: role of the gtp device was not specified\n");
+		return -1;
+	}
+
+	if (!GTP_ATTRSET(attrs, IFLA_GTP_PDP_HASHSIZE))
+		addattr32(n, 1024, IFLA_GTP_PDP_HASHSIZE, 1024);
+
+	return 0;
+}
+
+static void gtp_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
+{
+
+	if (tb[IFLA_GTP_ROLE]) {
+		__u32 role = rta_getattr_u32(tb[IFLA_GTP_ROLE]);
+
+		if (role == GTP_ROLE_SGSN)
+			print_string(PRINT_ANY, "role", "role %s ", "sgsn");
+		else
+			print_string(PRINT_ANY, "role", "role %s ", "ggsn");
+	}
+
+	if (tb[IFLA_GTP_PDP_HASHSIZE]) {
+		__u32 hsize = rta_getattr_u32(tb[IFLA_GTP_PDP_HASHSIZE]);
+
+		print_uint(PRINT_ANY, "hsize", "hsize %u ", hsize);
+	}
+}
+
+static void gtp_print_help(struct link_util *lu, int argc, char **argv,
+			   FILE *f)
+{
+	print_explain(f);
+}
+
+struct link_util gtp_link_util = {
+	.id		= "gtp",
+	.maxattr	= IFLA_GTP_MAX,
+	.parse_opt	= gtp_parse_opt,
+	.print_opt	= gtp_print_opt,
+	.print_help	= gtp_print_help,
+};
diff --git a/man/man8/ip-link.8.in b/man/man8/ip-link.8.in
index 19a0c9cab811..819ca8f7a330 100644
--- a/man/man8/ip-link.8.in
+++ b/man/man8/ip-link.8.in
@@ -233,7 +233,8 @@ ip-link \- network device configuration
 .BR macsec " |"
 .BR netdevsim " |"
 .BR rmnet " |"
-.BR xfrm " ]"
+.BR xfrm " |"
+.BR gtp " ]"
 
 .ti -8
 .IR ETYPE " := [ " TYPE " |"
@@ -382,6 +383,9 @@ Link types:
 .sp
 .BR xfrm
 - Virtual xfrm interface
+.sp
+.BR gtp
+- GPRS Tunneling Protocol
 .in -8
 
 .TP
@@ -1926,6 +1930,25 @@ policies. Policies must be configured with the same key. If not set, the key def
 
 .in -8
 
+.TP
+GTP Type Support
+For a link of type
+.I GTP
+the following additional arguments are supported:
+
+.BI "ip link add " DEVICE " type gtp role " ROLE " hsize " HSIZE
+
+.in +8
+.sp
+.BI role " ROLE "
+- specifies the role of the GTP device, either sgsn or ggsn
+
+.sp
+.BI hsize " HSIZE "
+- specifies size of the hashtable which stores PDP contexts
+
+.in -8
+
 .SS ip link delete - delete virtual link
 
 .TP
-- 
2.31.1

[PATCH iproute2-next 2/2] f_flower: Implement gtp options support

[Wojciech Drewek]

Add support for parsing TCA_FLOWER_KEY_ENC_OPTS_GTP.
Options are as follows: PDU_TYPE:QFI where each
option is represented as 8-bit hexadecimal value.

e.g.
  # ip link add gtp_dev type gtp role sgsn
  # tc qdisc add dev gtp_dev ingress
  # tc filter add dev gtp_dev protocol ip parent ffff: \
      flower \
        enc_key_id 11 \
        gtp_opts 1:8/ff:ff \
      action mirred egress redirect dev eth0

Signed-off-by: Wojciech Drewek <wojciech.drewek@intel.com>
---
 include/uapi/linux/pkt_cls.h |  16 +++++
 man/man8/tc-flower.8         |  10 +++
 tc/f_flower.c                | 120 +++++++++++++++++++++++++++++++++++
 3 files changed, 146 insertions(+)

diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
index ee38b35c3f57..30ff8da0631b 100644
--- a/include/uapi/linux/pkt_cls.h
+++ b/include/uapi/linux/pkt_cls.h
@@ -616,6 +616,10 @@ enum {
 					 * TCA_FLOWER_KEY_ENC_OPT_ERSPAN_
 					 * attributes
 					 */
+	TCA_FLOWER_KEY_ENC_OPTS_GTP,	/* Nested
+					 * TCA_FLOWER_KEY_ENC_OPT_GTP_
+					 * attributes
+					 */
 	__TCA_FLOWER_KEY_ENC_OPTS_MAX,
 };
 
@@ -654,6 +658,18 @@ enum {
 #define TCA_FLOWER_KEY_ENC_OPT_ERSPAN_MAX \
 		(__TCA_FLOWER_KEY_ENC_OPT_ERSPAN_MAX - 1)
 
+enum {
+	TCA_FLOWER_KEY_ENC_OPT_GTP_UNSPEC,
+	TCA_FLOWER_KEY_ENC_OPT_GTP_PDU_TYPE,		/* u8 */
+	TCA_FLOWER_KEY_ENC_OPT_GTP_QFI,			/* u8 */
+
+	__TCA_FLOWER_KEY_ENC_OPT_GTP_MAX,
+};
+
+#define TCA_FLOWER_KEY_ENC_OPT_GTP_MAX \
+		(__TCA_FLOWER_KEY_ENC_OPT_GTP_MAX - 1)
+
+
 enum {
 	TCA_FLOWER_KEY_MPLS_OPTS_UNSPEC,
 	TCA_FLOWER_KEY_MPLS_OPTS_LSE,
diff --git a/man/man8/tc-flower.8 b/man/man8/tc-flower.8
index 4541d9372684..f918a06d2927 100644
--- a/man/man8/tc-flower.8
+++ b/man/man8/tc-flower.8
@@ -89,6 +89,8 @@ flower \- flow based traffic control filter
 .B vxlan_opts
 |
 .B erspan_opts
+|
+.B gtp_opts
 }
 .IR OPTIONS " | "
 .BR ip_flags
@@ -411,6 +413,8 @@ Match the connection zone, and can be masked.
 .BI vxlan_opts " OPTIONS"
 .TQ
 .BI erspan_opts " OPTIONS"
+.TQ
+.BI gtp_opts " OPTIONS"
 Match on IP tunnel metadata. Key id
 .I NUMBER
 is a 32 bit tunnel key id (e.g. VNI for VXLAN tunnel).
@@ -446,6 +450,12 @@ VERSION:INDEX:DIR:HWID/VERSION:INDEX_MASK:DIR_MASK:HWID_MASK, where VERSION is
 represented as a 8bit number, INDEX as an 32bit number, DIR and HWID as a 8bit
 number. Multiple options is not supported. Note INDEX/INDEX_MASK is used when
 VERSION is 1, and DIR/DIR_MASK and HWID/HWID_MASK are used when VERSION is 2.
+gtp_opts
+.I OPTIONS
+doesn't support multiple options, and it consists of a key followed by a slash
+and corresponding mask. If the mask is missing, \fBtc\fR assumes a full-length
+match. The option can be described in the form PDU_TYPE:QFI/PDU_TYPE_MASK:QFI_MASK
+where both PDU_TYPE and QFI are represented as a 8bit hexadecimal values.
 .TP
 .BI ip_flags " IP_FLAGS"
 .I IP_FLAGS
diff --git a/tc/f_flower.c b/tc/f_flower.c
index 6d70b92a2894..eb234bc70484 100644
--- a/tc/f_flower.c
+++ b/tc/f_flower.c
@@ -1022,6 +1022,52 @@ static int flower_parse_erspan_opt(char *str, struct nlmsghdr *n)
 	return 0;
 }
 
+static int flower_parse_gtp_opt(char *str, struct nlmsghdr *n)
+{
+	struct rtattr *nest;
+	char *token;
+	int arg, err;
+
+	nest = addattr_nest(n, MAX_MSG, TCA_FLOWER_KEY_ENC_OPTS_GTP | NLA_F_NESTED);
+
+	token = strsep(&str, ":");
+	for (arg = 1; arg <= TCA_FLOWER_KEY_ENC_OPT_GTP_MAX; arg++) {
+		switch (arg) {
+		case TCA_FLOWER_KEY_ENC_OPT_GTP_PDU_TYPE:
+		{
+			__u8 pdu_type;
+
+			if (!strlen(token))
+				break;
+			err = get_u8(&pdu_type, token, 16);
+			if (err)
+				return err;
+			addattr8(n, MAX_MSG, arg, pdu_type);
+			break;
+		}
+		case TCA_FLOWER_KEY_ENC_OPT_GTP_QFI:
+		{
+			__u8 qfi;
+
+			if (!strlen(token))
+				break;
+			err = get_u8(&qfi, token, 16);
+			if (err)
+				return err;
+			addattr8(n, MAX_MSG, arg, qfi);
+			break;
+		}
+		default:
+			fprintf(stderr, "Unknown \"gtp_opts\" type\n");
+			return -1;
+		}
+		token = strsep(&str, ":");
+	}
+	addattr_nest_end(n, nest);
+
+	return 0;
+}
+
 static int flower_parse_geneve_opts(char *str, struct nlmsghdr *n)
 {
 	char *token;
@@ -1205,6 +1251,41 @@ static int flower_parse_enc_opts_erspan(char *str, struct nlmsghdr *n)
 	return 0;
 }
 
+static int flower_parse_enc_opts_gtp(char *str, struct nlmsghdr *n)
+{
+	char key[XATTR_SIZE_MAX], mask[XATTR_SIZE_MAX];
+	struct rtattr *nest;
+	char *slash;
+	int err;
+
+	slash = strchr(str, '/');
+	if (slash) {
+		*slash++ = '\0';
+		if (strlen(slash) > XATTR_SIZE_MAX)
+			return -1;
+		strcpy(mask, slash);
+	} else
+		strcpy(mask, "ff:ff");
+
+	if (strlen(str) > XATTR_SIZE_MAX)
+		return -1;
+	strcpy(key, str);
+
+	nest = addattr_nest(n, MAX_MSG, TCA_FLOWER_KEY_ENC_OPTS | NLA_F_NESTED);
+	err = flower_parse_gtp_opt(key, n);
+	if (err)
+		return err;
+	addattr_nest_end(n, nest);
+
+	nest = addattr_nest(n, MAX_MSG, TCA_FLOWER_KEY_ENC_OPTS_MASK | NLA_F_NESTED);
+	err = flower_parse_gtp_opt(mask, n);
+	if (err)
+		return err;
+	addattr_nest_end(n, nest);
+
+	return 0;
+}
+
 static int flower_parse_mpls_lse(int *argc_p, char ***argv_p,
 				 struct nlmsghdr *nlh)
 {
@@ -1857,6 +1938,13 @@ static int flower_parse_opt(struct filter_util *qu, char *handle,
 				fprintf(stderr, "Illegal \"erspan_opts\"\n");
 				return -1;
 			}
+		} else if (matches(*argv, "gtp_opts") == 0) {
+			NEXT_ARG();
+			ret = flower_parse_enc_opts_gtp(*argv, n);
+			if (ret < 0) {
+				fprintf(stderr, "Illegal \"gtp_opts\"\n");
+				return -1;
+			}
 		} else if (matches(*argv, "action") == 0) {
 			NEXT_ARG();
 			ret = parse_action(&argc, &argv, TCA_FLOWER_ACT, n);
@@ -2342,6 +2430,28 @@ static void flower_print_erspan_opts(const char *name, struct rtattr *attr,
 	sprintf(strbuf, "%u:%u:%u:%u", ver, idx, dir, hwid);
 }
 
+static void flower_print_gtp_opts(const char *name, struct rtattr *attr,
+				  char *strbuf)
+{
+	struct rtattr *tb[TCA_FLOWER_KEY_ENC_OPT_GTP_MAX + 1];
+	__u8 pdu_type, qfi;
+
+	parse_rtattr(tb, TCA_FLOWER_KEY_ENC_OPT_GTP_MAX, RTA_DATA(attr),
+		     RTA_PAYLOAD(attr));
+
+	pdu_type = rta_getattr_u8(tb[TCA_FLOWER_KEY_ENC_OPT_GTP_PDU_TYPE]);
+	qfi = rta_getattr_u8(tb[TCA_FLOWER_KEY_ENC_OPT_GTP_QFI]);
+
+	open_json_array(PRINT_JSON, name);
+	open_json_object(NULL);
+	print_uint(PRINT_JSON, "pdu_type", NULL, pdu_type);
+	print_uint(PRINT_JSON, "qfi", NULL, qfi);
+	close_json_object();
+	close_json_array(PRINT_JSON, name);
+
+	sprintf(strbuf, "%02x:%02x", pdu_type, qfi);
+}
+
 static void flower_print_enc_parts(const char *name, const char *namefrm,
 				   struct rtattr *attr, char *key, char *mask)
 {
@@ -2418,6 +2528,16 @@ static void flower_print_enc_opts(const char *name, struct rtattr *attr,
 
 		flower_print_enc_parts(name, "  erspan_opts %s", attr, key,
 				       msk);
+	} else if (key_tb[TCA_FLOWER_KEY_ENC_OPTS_GTP]) {
+		flower_print_gtp_opts("gtp_opt_key",
+				      key_tb[TCA_FLOWER_KEY_ENC_OPTS_GTP], key);
+
+		if (msk_tb[TCA_FLOWER_KEY_ENC_OPTS_GTP])
+			flower_print_gtp_opts("gtp_opt_mask",
+					      msk_tb[TCA_FLOWER_KEY_ENC_OPTS_GTP], msk);
+
+		flower_print_enc_parts(name, "  gtp_opts %s", attr, key,
+				       msk);
 	}
 
 	free(msk);
-- 
2.31.1

Re: [PATCH iproute2-next 1/2] ip: GTP support in ip link

[Stephen Hemminger]

On Thu, 27 Jan 2022 14:13:54 +0100
Wojciech Drewek <wojciech.drewek@intel.com> wrote:

> +/*
> + * iplink_gtp.c	GTP device support
> + *
> + *		This program is free software; you can redistribute it and/or
> + *		modify it under the terms of the GNU General Public License
> + *		as published by the Free Software Foundation; either version
> + *		2 of the License, or (at your option) any later version.
> + *
> + * Authors:	Wojciech Drewek <wojciech.drewek@intel.com>
> + */

Please just us SPDX tag instead of boilerplate for all new code.

Re: [PATCH iproute2-next 1/2] ip: GTP support in ip link

[Stephen Hemminger]

On Thu, 27 Jan 2022 14:13:54 +0100
Wojciech Drewek <wojciech.drewek@intel.com> wrote:

> +		if (!matches(*argv, "role")) 

Matches() is a bug trap. Please use strcmp instead.

Re: [PATCH iproute2-next 1/2] ip: GTP support in ip link

[Stephen Hemminger]

On Thu, 27 Jan 2022 14:13:54 +0100
Wojciech Drewek <wojciech.drewek@intel.com> wrote:

> +		if (role == GTP_ROLE_SGSN)
> +			print_string(PRINT_ANY, "role", "role %s ", "sgsn");
> +		else
> +			print_string(PRINT_ANY, "role", "role %s ", "ggsn");

Why not us trigraph?
		print_string(PRINT_ANY, "role", "role %s ",
				role == GTP_ROLE_SGSN ? "sgsn" : "ggsn");

Re: [PATCH iproute2-next 2/2] f_flower: Implement gtp options support

[Stephen Hemminger]

On Thu, 27 Jan 2022 14:13:55 +0100
Wojciech Drewek <wojciech.drewek@intel.com> wrote:

> +	open_json_array(PRINT_JSON, name);
> +	open_json_object(NULL);
> +	print_uint(PRINT_JSON, "pdu_type", NULL, pdu_type);
> +	print_uint(PRINT_JSON, "qfi", NULL, qfi);
> +	close_json_object();
> +	close_json_array(PRINT_JSON, name);
> +
> +	sprintf(strbuf, "%02x:%02x", pdu_type, qfi);

Doing JSON specific code is not necessary here?
And why an array of two named elements? Seems confusing

RE: [PATCH iproute2-next 2/2] f_flower: Implement gtp options support

[Drewek, Wojciech]

Hi Stephen,

I was just following the approach used for other options but it looks like that
JSON specific code is not needed. I 'll get rid of it in next version.

Regards,
Wojtek

> -----Original Message-----
> From: Stephen Hemminger <stephen@networkplumber.org>
> Sent: czwartek, 27 stycznia 2022 18:16
> To: Drewek, Wojciech <wojciech.drewek@intel.com>
> Cc: netdev@vger.kernel.org; dsahern@gmail.com; michal.swiatkowski@linux.intel.com; marcin.szycik@linux.intel.com
> Subject: Re: [PATCH iproute2-next 2/2] f_flower: Implement gtp options support
> 
> On Thu, 27 Jan 2022 14:13:55 +0100
> Wojciech Drewek <wojciech.drewek@intel.com> wrote:
> 
> > +	open_json_array(PRINT_JSON, name);
> > +	open_json_object(NULL);
> > +	print_uint(PRINT_JSON, "pdu_type", NULL, pdu_type);
> > +	print_uint(PRINT_JSON, "qfi", NULL, qfi);
> > +	close_json_object();
> > +	close_json_array(PRINT_JSON, name);
> > +
> > +	sprintf(strbuf, "%02x:%02x", pdu_type, qfi);
> 
> Doing JSON specific code is not necessary here?
> And why an array of two named elements? Seems confusing

RE: [PATCH iproute2-next 1/2] ip: GTP support in ip link

[Drewek, Wojciech]

> -----Original Message-----
> From: Stephen Hemminger <stephen@networkplumber.org>
> Sent: czwartek, 27 stycznia 2022 18:14
> To: Drewek, Wojciech <wojciech.drewek@intel.com>
> Cc: netdev@vger.kernel.org; dsahern@gmail.com; michal.swiatkowski@linux.intel.com; marcin.szycik@linux.intel.com
> Subject: Re: [PATCH iproute2-next 1/2] ip: GTP support in ip link
> 
> On Thu, 27 Jan 2022 14:13:54 +0100
> Wojciech Drewek <wojciech.drewek@intel.com> wrote:
> 
> > +		if (role == GTP_ROLE_SGSN)
> > +			print_string(PRINT_ANY, "role", "role %s ", "sgsn");
> > +		else
> > +			print_string(PRINT_ANY, "role", "role %s ", "ggsn");
> 
> Why not us trigraph?
> 		print_string(PRINT_ANY, "role", "role %s ",
> 				role == GTP_ROLE_SGSN ? "sgsn" : "ggsn");
Just not a big fan of it, I'm not used to using it. It might look smooth here though.