From 863f0cafefd9293451fe4682b02c8186a68ad30a Mon Sep 17 00:00:00 2001
From: Phil Sutter <psutter@redhat.com>
Date: Thu, 18 Feb 2016 14:19:36 +0100
Subject: [PATCH] ip: route: add congestion control metric

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1291832
Upstream Status: iproute2.git commit 6ef87f9cce213

commit 6ef87f9cce213cae66098d08e0abc36d67b95244
Author: Daniel Borkmann <dborkman@redhat.com>
Date:   Fri Jan 9 00:13:06 2015 +0100

    ip: route: add congestion control metric

    This patch adds configuration and dumping of congestion control metric
    for ip route, for example:

      ip route add <dst> dev foo congctl [lock] dctcp

    Reference: http://thread.gmane.org/gmane.linux.network/344733
    Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
---
 ip/iproute.c           | 22 ++++++++++++++++++----
 man/man8/ip-route.8.in | 19 ++++++++++++++++++-
 2 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/ip/iproute.c b/ip/iproute.c
index ea69aa3..d3a5e1c 100644
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -53,6 +53,7 @@ static const char *mx_names[RTAX_MAX+1] = {
 	[RTAX_RTO_MIN]	= "rto_min",
 	[RTAX_INITRWND]	= "initrwnd",
 	[RTAX_QUICKACK]	= "quickack",
+	[RTAX_CC_ALGO]	= "congctl",
 };
 static void usage(void) __attribute__((noreturn));
 
@@ -80,8 +81,7 @@ static void usage(void)
 	fprintf(stderr, "           [ window NUMBER] [ cwnd NUMBER ] [ initcwnd NUMBER ]\n");
 	fprintf(stderr, "           [ ssthresh NUMBER ] [ realms REALM ] [ src ADDRESS ]\n");
 	fprintf(stderr, "           [ rto_min TIME ] [ hoplimit NUMBER ] [ initrwnd NUMBER ]\n");
-	fprintf(stderr, "           [ features FEATURES ]\n");
-	fprintf(stderr, "           [ quickack BOOL ]\n");
+	fprintf(stderr, "           [ features FEATURES ] [ quickack BOOL ] [ congctl NAME ]\n");
 	fprintf(stderr, "TYPE := [ unicast | local | broadcast | multicast | throw |\n");
 	fprintf(stderr, "          unreachable | prohibit | blackhole | nat ]\n");
 	fprintf(stderr, "TABLE_ID := [ local | main | default | all | NUMBER ]\n");
@@ -539,7 +539,7 @@ int print_route(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
 			mxlock = *(unsigned*)RTA_DATA(mxrta[RTAX_LOCK]);
 
 		for (i=2; i<= RTAX_MAX; i++) {
-			unsigned val;
+			__u32 val;
 
 			if (mxrta[i] == NULL)
 				continue;
@@ -548,10 +548,12 @@ int print_route(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
 				fprintf(fp, " %s", mx_names[i]);
 			else
 				fprintf(fp, " metric %d", i);
+
 			if (mxlock & (1<<i))
 				fprintf(fp, " lock");
+			if (i != RTAX_CC_ALGO)
+				val = rta_getattr_u32(mxrta[i]);
 
-			val = *(unsigned*)RTA_DATA(mxrta[i]);
 			switch (i) {
 			case RTAX_FEATURES:
 				print_rtax_features(fp, val);
@@ -576,6 +578,10 @@ int print_route(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
 					fprintf(fp, " %gs", val/1e3);
 				else
 					fprintf(fp, " %ums", val);
+				break;
+			case RTAX_CC_ALGO:
+				fprintf(fp, " %s", rta_getattr_str(mxrta[i]));
+				break;
 			}
 		}
 	}
@@ -928,6 +934,14 @@ static int iproute_modify(int cmd, unsigned flags, int argc, char **argv)
 			if (quickack != 1 && quickack != 0)
 				invarg("\"quickack\" value should be 0 or 1\n", *argv);
 			rta_addattr32(mxrta, sizeof(mxbuf), RTAX_QUICKACK, quickack);
+		} else if (matches(*argv, "congctl") == 0) {
+			NEXT_ARG();
+			if (strcmp(*argv, "lock") == 0) {
+				mxlock |= 1 << RTAX_CC_ALGO;
+				NEXT_ARG();
+			}
+			rta_addattr_l(mxrta, sizeof(mxbuf), RTAX_CC_ALGO, *argv,
+				      strlen(*argv));
 		} else if (matches(*argv, "rttvar") == 0) {
 			unsigned win;
 			NEXT_ARG();
diff --git a/man/man8/ip-route.8.in b/man/man8/ip-route.8.in
index 05fd879..ec4a5b2 100644
--- a/man/man8/ip-route.8.in
+++ b/man/man8/ip-route.8.in
@@ -116,7 +116,9 @@ replace " } "
 .B  features
 .IR FEATURES " ] [ "
 .B  quickack
-.IR BOOL " ]"
+.IR BOOL " ] [ "
+.B  congctl
+.IR NAME " ]"
 
 .ti -8
 .IR TYPE " := [ "
@@ -433,6 +435,21 @@ sysctl is set to 0.
 Enable or disable quick ack for connections to this destination.
 
 .TP
+.BI congctl " NAME " "(3.20+ only)"
+.TP
+.BI "congctl lock" " NAME " "(3.20+ only)"
+Sets a specific TCP congestion control algorithm only for a given destination.
+If not specified, Linux keeps the current global default TCP congestion control
+algorithm, or the one set from the application. If the modifier
+.B lock
+is not used, an application may nevertheless overwrite the suggested congestion
+control algorithm for that destination. If the modifier
+.B lock
+is used, then an application is not allowed to overwrite the specified congestion
+control algorithm for that destination, thus it will be enforced/guaranteed to
+use the proposed algorithm.
+
+.TP
 .BI advmss " NUMBER " "(2.3.15+ only)"
 the MSS ('Maximal Segment Size') to advertise to these
 destinations when establishing TCP connections. If it is not given,
-- 
1.8.3.1