Date: Mon, 20 Nov 2000 22:41:41 +0100 From: Jesper Skriver <jesper@skriver.dk> To: "Louis A. Mamakos" <louie@TransSys.COM> Cc: hackers@FreeBSD.ORG Subject: Re: React to ICMP administratively prohibited ? Message-ID: <20001120224141.A80979@skriver.dk> In-Reply-To: <200011192301.eAJN15714300@whizzo.transsys.com>; from louie@TransSys.COM on Sun, Nov 19, 2000 at 06:01:05PM -0500 References: <20001118155446.A81075@skriver.dk> <Pine.BSF.4.21.0011181102540.52996-100000@achilles.silby.com> <20001118183632.A99512@skriver.dk> <20001119215357.A41281@skriver.dk> <200011192103.eAJL34713541@whizzo.transsys.com> <20001119220451.B41281@skriver.dk> <20001119223818.A79237@skriver.dk> <200011192301.eAJN15714300@whizzo.transsys.com>
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On Sun, Nov 19, 2000 at 06:01:05PM -0500, Louis A. Mamakos wrote:
>
> It would seem more appropriate, somehow, to push the response to the
> ICMP message up into the protocols where they can take the appropriate
> action. Of course, the problem is that the PRC_* abstracted codes may
> not be rich enough to express all the semantics you'd wish to convey.
>
> So one goal might be to see if this sort of process could get pushed into
> netinet/tcp_sub.c:tcp_ctlinput(). Personally, I don't really like the
> idea of the icmp_input() function reaching into TCP's private state and
> doing stuff.
So what you propose is to let netinet/ip_icmp.c all alone, and do something
like the below in netinet/tcp_sub.c:tcp_ctlinput()
else if ((icmp_admin_prohib_like_rst == 1) && ((cmd == ICMP_UNREACH_NET_PROHIB) ||
(cmd == ICMP_UNREACH_HOST_PROHIB) || (cmd == ICMP_UNREACH_FILTER_PROHIB)) && (ip))
notify = tcp_drop_syn_sent;
instead of
else if ((icmp_admin_prohib_like_rst == 1) && (cmd == PRC_UNREACH_PORT) && (ip))
notify = tcp_drop_syn_sent;
correct ?
Is this ok - from my vague understanding of this part of the code, I
thought I had to use the PRC_* abstracted codes ...
> There's too many potential interactions (e.g., what about
> IPSEC security associations?)
Dunno, know very little of IPsec ...
Latest diff attached, this implement a sysctl,
'net.inet.tcp.icmp_admin_prohib_like_rst' which default to being
disabled.
/Jesper
--
Jesper Skriver, jesper(at)skriver(dot)dk - CCIE #5456
Work: Network manager @ AS3292 (Tele Danmark DataNetworks)
Private: Geek @ AS2109 (A much smaller network ;-)
One Unix to rule them all, One Resolver to find them,
One IP to bring them all and in the zone to bind them.
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diff -ru sys/netinet.old/ip_icmp.c sys/netinet/ip_icmp.c
--- sys/netinet.old/ip_icmp.c Thu Nov 2 10:46:23 2000
+++ sys/netinet/ip_icmp.c Mon Nov 20 22:33:43 2000
@@ -328,6 +328,11 @@
case ICMP_UNREACH_NET_UNKNOWN:
case ICMP_UNREACH_NET_PROHIB:
+ if (icp->icmp_ip.ip_p == IPPROTO_TCP) {
+ code = PRC_UNREACH_PORT;
+ break;
+ }
+
case ICMP_UNREACH_TOSNET:
code = PRC_UNREACH_NET;
break;
@@ -335,11 +340,21 @@
case ICMP_UNREACH_HOST_UNKNOWN:
case ICMP_UNREACH_ISOLATED:
case ICMP_UNREACH_HOST_PROHIB:
+ if (icp->icmp_ip.ip_p == IPPROTO_TCP) {
+ code = PRC_UNREACH_PORT;
+ break;
+ }
+
case ICMP_UNREACH_TOSHOST:
code = PRC_UNREACH_HOST;
break;
case ICMP_UNREACH_FILTER_PROHIB:
+ if (icp->icmp_ip.ip_p == IPPROTO_TCP) {
+ code = PRC_UNREACH_PORT;
+ break;
+ }
+
case ICMP_UNREACH_HOST_PRECEDENCE:
case ICMP_UNREACH_PRECEDENCE_CUTOFF:
code = PRC_UNREACH_PORT;
diff -ru sys/netinet.old/tcp_subr.c sys/netinet/tcp_subr.c
--- sys/netinet.old/tcp_subr.c Fri Oct 27 13:45:41 2000
+++ sys/netinet/tcp_subr.c Mon Nov 20 22:33:48 2000
@@ -134,6 +134,14 @@
SYSCTL_INT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_RD,
&tcbinfo.ipi_count, 0, "Number of active PCBs");
+/*
+ * React to ICMP administratively prohibited
+ */
+
+static int icmp_admin_prohib_like_rst = 0;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, icmp_admin_prohib_like_rst, CTLFLAG_RW,
+ &icmp_admin_prohib_like_rst, 0, "Treat ICMP administratively prohibited messages like TCP RST.");
+
static void tcp_cleartaocache __P((void));
static void tcp_notify __P((struct inpcb *, int));
@@ -961,6 +969,8 @@
if (cmd == PRC_QUENCH)
notify = tcp_quench;
+ else if ((icmp_admin_prohib_like_rst == 1) && (cmd == PRC_UNREACH_PORT) && (ip))
+ notify = tcp_drop_syn_sent;
else if (cmd == PRC_MSGSIZE)
notify = tcp_mtudisc;
else if (!PRC_IS_REDIRECT(cmd) &&
@@ -1071,6 +1081,20 @@
if (tp)
tp->snd_cwnd = tp->t_maxseg;
+}
+
+/*
+ * When a ICMP unreachable is recieved, drop the
+ * TCP connection, but only if in SYN SENT
+ */
+void
+tcp_drop_syn_sent(inp, errno)
+ struct inpcb *inp;
+ int errno;
+{
+ struct tcpcb *tp = intotcpcb(inp);
+ if((tp) && (tp->t_state == TCPS_SYN_SENT))
+ tcp_drop(tp, errno);
}
/*
diff -ru sys/netinet.old/tcp_var.h sys/netinet/tcp_var.h
--- sys/netinet.old/tcp_var.h Sat Jul 22 01:26:37 2000
+++ sys/netinet/tcp_var.h Sun Nov 19 21:17:55 2000
@@ -387,6 +387,7 @@
void tcp_input __P((struct mbuf *, int, int));
void tcp_mss __P((struct tcpcb *, int));
int tcp_mssopt __P((struct tcpcb *));
+void tcp_drop_syn_sent __P((struct inpcb *, int));
void tcp_mtudisc __P((struct inpcb *, int));
struct tcpcb *
tcp_newtcpcb __P((struct inpcb *));
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