git: 8aafae66394f - main - traceroute: Implement ECN bleaching detection
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Date: Wed, 03 Jan 2024 18:32:59 UTC
The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=8aafae66394fe64489d6371c22da5a5fb7ee7c81 commit 8aafae66394fe64489d6371c22da5a5fb7ee7c81 Author: Jose Luis Duran <jlduran@gmail.com> AuthorDate: 2023-10-28 00:28:52 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2024-01-03 17:57:54 +0000 traceroute: Implement ECN bleaching detection Explicit Congestion Notification (ECN) is a mechanism that allows end-to-end notification of network congestion without dropping packets by explicitly setting the ECN code point (2 bits). Per RFC 8087, section 3.5, network devices should not be configured to change the ECN code point in the packets that they forward, except to set the CE (Congestion Experienced) code point ('11') to signal incipient congestion. The current commit adds an -E flag to traceroute that crafts a packet with an ECT(1) code point ('01'). If the packet is received back with a zero ECN code point ('00'), it outputs that the hop in question erases or "bleaches" the ECN code point values. Bleaching may occur for various reasons (including normalizing packets to hide which equipment supports ECN). This policy prevents the use of ECN by applications. If the packet is received back with an all-ones ECN code point ('11'), it outputs that the hop in question is experiencing "congestion". If the packet is received back with a different ECN code point ('10'), it outputs that the hop in question changes or "mangles" the ECN code point values. If the packet is received with the same ECN code point that was sent ('01'), it outputs that the hop has "passed" the ECN bits appropriately. Inspired by: Darwin Reviewed by: imp, markj MFC after: 1 month Pull Request: https://github.com/freebsd/freebsd-src/pull/879 --- contrib/traceroute/traceroute.8 | 20 ++++++++++++++++++-- contrib/traceroute/traceroute.c | 30 ++++++++++++++++++++++++++++-- 2 files changed, 46 insertions(+), 4 deletions(-) diff --git a/contrib/traceroute/traceroute.8 b/contrib/traceroute/traceroute.8 index d177413738dc..804306a11ca6 100644 --- a/contrib/traceroute/traceroute.8 +++ b/contrib/traceroute/traceroute.8 @@ -15,7 +15,7 @@ .\" .\" $Id: traceroute.8,v 1.19 2000/09/21 08:44:19 leres Exp $ .\" -.Dd November 25, 2020 +.Dd October 25, 2023 .Dt TRACEROUTE 8 .Os .Sh NAME @@ -24,7 +24,7 @@ .Sh SYNOPSIS .Nm .Bk -words -.Op Fl adDeFISnrvx +.Op Fl adDeEFISnrvx .Op Fl f Ar first_ttl .Op Fl g Ar gateway .Op Fl M Ar first_ttl @@ -66,6 +66,22 @@ default. Firewall evasion mode. Use fixed destination ports for UDP, UDP-Lite, TCP and SCTP probes. The destination port does NOT increment with each packet sent. +.It Fl E +Detect ECN bleaching. +Set the +.Em IPTOS_ECN_ECT1 +Explicit Congestion Notification (ECN) bits +.Pq Dv 01 , +and report if the hop has bleached +.Pq Dv 00 +or mangled +.Pq Dv 10 +them, or if it is experiencing congestion +.Pq Dv 11 . +Otherwise, report that it passed the bits appropriately. +If +.Fl t +is also specified, the corresponding ECN bits will be replaced. .It Fl f Ar first_ttl Set the initial time-to-live used in the first outgoing probe packet. .It Fl F diff --git a/contrib/traceroute/traceroute.c b/contrib/traceroute/traceroute.c index 282d4b2af929..03135e39837f 100644 --- a/contrib/traceroute/traceroute.c +++ b/contrib/traceroute/traceroute.c @@ -365,6 +365,7 @@ int doipcksum = 1; /* calculate ip checksums by default */ int optlen; /* length of ip options */ int fixedPort = 0; /* Use fixed destination port for TCP and UDP */ int printdiff = 0; /* Print the difference between sent and quoted */ +int ecnflag = 0; /* ECN bleaching detection flag */ extern int optind; extern int opterr; @@ -597,7 +598,7 @@ main(int argc, char **argv) prog = argv[0]; opterr = 0; - while ((op = getopt(argc, argv, "aA:edDFInrSvxf:g:i:M:m:P:p:q:s:t:w:z:")) != EOF) + while ((op = getopt(argc, argv, "aA:eEdDFInrSvxf:g:i:M:m:P:p:q:s:t:w:z:")) != EOF) switch (op) { case 'a': as_path = 1; @@ -620,6 +621,10 @@ main(int argc, char **argv) fixedPort = 1; break; + case 'E': + ecnflag = 1; + break; + case 'f': case 'M': /* FreeBSD compat. */ first_ttl = str2val(optarg, "first ttl", 1, 255); @@ -784,6 +789,10 @@ main(int argc, char **argv) outip->ip_v = IPVERSION; if (settos) outip->ip_tos = tos; + if (ecnflag) { + outip->ip_tos &= ~IPTOS_ECN_MASK; + outip->ip_tos |= IPTOS_ECN_ECT1; + } #ifdef BYTESWAP_IP_HDR outip->ip_len = htons(packlen); outip->ip_off = htons(off); @@ -1122,6 +1131,23 @@ main(int argc, char **argv) #endif precis = 3; Printf(" %.*f ms", precis, T); + if (ecnflag) { + u_char ecn = hip->ip_tos & IPTOS_ECN_MASK; + switch (ecn) { + case IPTOS_ECN_ECT1: + Printf(" (ecn=passed)"); + break; + case IPTOS_ECN_NOTECT: + Printf(" (ecn=bleached)"); + break; + case IPTOS_ECN_CE: + Printf(" (ecn=congested)"); + break; + default: + Printf(" (ecn=mangled)"); + break; + } + } if (printdiff) { Printf("\n"); Printf("%*.*s%s\n", @@ -2126,7 +2152,7 @@ usage(void) Fprintf(stderr, "Version %s\n", version); Fprintf(stderr, - "Usage: %s [-adDeFInrSvx] [-f first_ttl] [-g gateway] [-i iface]\n" + "Usage: %s [-adDeEFInrSvx] [-f first_ttl] [-g gateway] [-i iface]\n" "\t[-m max_ttl] [-p port] [-P proto] [-q nqueries] [-s src_addr]\n" "\t[-t tos] [-w waittime] [-A as_server] [-z pausemsecs] host [packetlen]\n", prog); exit(1);