bgpd: Allow bgp to control the DSCP session TOS value

Allow BGP to control the TOS DSCP value in the tcp header
via a new command at the bgp global level `bgp session-dscp <0-63>`

Signed-off-by: Donald Sharp <sharpd@nvidia.com>
Signed-off-by: Pavel Shirhov <pavelsh@microsoft.com>

bgpd/bgp_network.c

@@ -741,11 +741,9 @@ int bgp_connect(struct peer *peer)
 #ifdef IPTOS_PREC_INTERNETCONTROL
 	frr_with_privs(&bgpd_privs) {
 		if (sockunion_family(&peer->su) == AF_INET)
-			setsockopt_ipv4_tos(peer->fd,
+			setsockopt_ipv4_tos(peer->fd, bm->tcp_dscp);
-					    IPTOS_PREC_INTERNETCONTROL);
 		else if (sockunion_family(&peer->su) == AF_INET6)
-			setsockopt_ipv6_tclass(peer->fd,
+			setsockopt_ipv6_tclass(peer->fd, bm->tcp_dscp);
-					       IPTOS_PREC_INTERNETCONTROL);
 	}
 #endif
 
@@ -822,10 +820,9 @@ static int bgp_listener(int sock, struct sockaddr *sa, socklen_t salen,
 
 #ifdef IPTOS_PREC_INTERNETCONTROL
 		if (sa->sa_family == AF_INET)
-			setsockopt_ipv4_tos(sock, IPTOS_PREC_INTERNETCONTROL);
+			setsockopt_ipv4_tos(sock, bm->tcp_dscp);
 		else if (sa->sa_family == AF_INET6)
-			setsockopt_ipv6_tclass(sock,
+			setsockopt_ipv6_tclass(sock, bm->tcp_dscp);
-					       IPTOS_PREC_INTERNETCONTROL);
 #endif
 
 		sockopt_v6only(sa->sa_family, sock);

bgpd/bgp_vty.c

@@ -1568,6 +1568,32 @@ DEFUN (no_router_bgp,
 	return CMD_SUCCESS;
 }
 
+/* bgp session-dscp */
+
+DEFPY (bgp_session_dscp,
+       bgp_session_dscp_cmd,
+       "bgp session-dscp (0-63)$dscp",
+       BGP_STR
+       "Override default (C6) bgp TCP session DSCP value\n"
+       "Manually configured dscp parameter\n")
+{
+	bm->tcp_dscp = dscp << 2;
+
+	return CMD_SUCCESS;
+}
+
+DEFPY (no_bgp_session_dscp,
+       no_bgp_session_dscp_cmd,
+       "no bgp session-dscp [(0-63)]",
+       NO_STR
+       BGP_STR
+       "Override default (C6) bgp TCP session DSCP value\n"
+       "Manually configured dscp parameter\n")
+{
+	bm->tcp_dscp = IPTOS_PREC_INTERNETCONTROL;
+
+	return CMD_SUCCESS;
+}
 
 /* BGP router-id.  */
 
@@ -17126,6 +17152,10 @@ int bgp_config_write(struct vty *vty)
 	if (CHECK_FLAG(bm->flags, BM_FLAG_SEND_EXTRA_DATA_TO_ZEBRA))
 		vty_out(vty, "bgp send-extra-data zebra\n");
 
+	/* BGP session DSCP value */
+	if (bm->tcp_dscp != IPTOS_PREC_INTERNETCONTROL)
+		vty_out(vty, "bgp session-dscp %u\n", bm->tcp_dscp >> 2);
+
 	/* BGP configuration. */
 	for (ALL_LIST_ELEMENTS(bm->bgp, mnode, mnnode, bgp)) {
 
@@ -17829,6 +17859,10 @@ void bgp_vty_init(void)
 	/* "no router bgp" commands. */
 	install_element(CONFIG_NODE, &no_router_bgp_cmd);
 
+	/* "bgp session-dscp command */
+	install_element(CONFIG_NODE, &bgp_session_dscp_cmd);
+	install_element(CONFIG_NODE, &no_bgp_session_dscp_cmd);
+
 	/* "bgp router-id" commands. */
 	install_element(BGP_NODE, &bgp_router_id_cmd);
 	install_element(BGP_NODE, &no_bgp_router_id_cmd);

bgpd/bgpd.c

@@ -3259,7 +3259,6 @@ static struct bgp *bgp_create(as_t *as, const char *name,
 
 	bgp->evpn_info = XCALLOC(MTYPE_BGP_EVPN_INFO,
 				 sizeof(struct bgp_evpn_info));
-
 	bgp_evpn_init(bgp);
 	bgp_evpn_vrf_es_init(bgp);
 	bgp_pbr_init(bgp);
@@ -7854,6 +7853,7 @@ void bgp_master_init(struct thread_master *master, const int buffer_size,
 	bm->terminating = false;
 	bm->socket_buffer = buffer_size;
 	bm->wait_for_fib = false;
+	bm->tcp_dscp = IPTOS_PREC_INTERNETCONTROL;
 
 	bgp_mac_init();
 	/* init the rd id space.

bgpd/bgpd.h

@@ -171,6 +171,10 @@ struct bgp_master {
 #define BM_FLAG_SEND_EXTRA_DATA_TO_ZEBRA (1 << 1)
 
 	bool terminating;	/* global flag that sigint terminate seen */
+
+	/* DSCP value for TCP sessions */
+	uint8_t tcp_dscp;
+
 	QOBJ_FIELDS;
 };
 DECLARE_QOBJ_TYPE(bgp_master);

doc/user/bgp.rst

@@ -4014,6 +4014,11 @@ behavior in BGP is not to send this data. If the routes were sent to zebra and
 the option is changed, bgpd doesn't reinstall the routes to comply with the new
 setting.
 
+.. clicmd:: bgp session-dscp (0-63)
+
+This command allows bgp to control, at a global level, the TCP dscp values
+in the TCP header.
+
 .. _bgp-suppress-fib:
 
 Suppressing routes not installed in FIB