File _service:tar_scm:backport-pppd-Negotiate-IP-add... of Package ppp

File _service:tar_scm:backport-pppd-Negotiate-IP-address-when-only-peer-addresses-are-provided.patch of Package ppp (Revision f651d441be9a2a20d5cb4fb4f75f212b)

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From a2094eba2406392a7bb69b436155e2d08ea555e8 Mon Sep 17 00:00:00 2001
From: pali <7141871+pali@users.noreply.github.com>
Date: Tue, 26 Jan 2021 03:55:25 +0100
Subject: [PATCH] pppd: Negotiate IP address when only peer addresses are
 provided (#236)
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This fixes special case when both ppp ends are configured to send only IP
address of other side and do not send its own IP address. Such setup is
correct because both ends can exchange its IP addresses and therefore they
have full information, they known both local and remote address.

This issue can be triggered by calling pppd with arguments:

./pppd debug local noauth nolock nodetach asyncmap 0 default-asyncmap novj noaccomp nopcomp nodeflate nobsdcomp nomagic noipv6 noipdefault nosendip :10.0.0.1 pty "./pppd debug local noauth nolock nodetach asyncmap 0 default-asyncmap novj noaccomp nopcomp nodeflate nobsdcomp nomagic noipv6 nosendip nodefaultroute :10.0.0.2 notty"

Without this patch IP addresses are not exchanges at all and pppd fails:

After applying this patch exchanging of IP addresses is working fine:

rcvd [LCP ConfReq id=0x1]
    sent [LCP ConfReq id=0x1]
    sent [LCP ConfAck id=0x1]
    rcvd [LCP ConfAck id=0x1]
    sent [LCP EchoReq id=0x0 magic=0x0]
    sent [IPCP ConfReq id=0x1]
    rcvd [LCP EchoReq id=0x0 magic=0x0]
    sent [LCP EchoRep id=0x0 magic=0x0]
    rcvd [IPCP ConfReq id=0x1]
    sent [IPCP ConfNak id=0x1 <addr 10.0.0.1>]
    rcvd [LCP EchoRep id=0x0 magic=0x0]
    rcvd [IPCP ConfNak id=0x1 <addr 10.0.0.2>]
    sent [IPCP ConfReq id=0x2 <addr 10.0.0.2>]
    rcvd [IPCP ConfReq id=0x2 <addr 10.0.0.1>]
    sent [IPCP ConfAck id=0x2 <addr 10.0.0.1>]
    rcvd [IPCP ConfAck id=0x2 <addr 10.0.0.2>]
    local  IP address 10.0.0.2
    remote IP address 10.0.0.1

Signed-off-by: Pali Rohár <pali@kernel.org>
---
 pppd/ipcp.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/pppd/ipcp.c b/pppd/ipcp.c
index fcf17b1e..d17dbd28 100644
--- a/pppd/ipcp.c
+++ b/pppd/ipcp.c
@@ -678,8 +678,9 @@ ipcp_resetci(fsm *f)
     ipcp_options *go = &ipcp_gotoptions[f->unit];
     ipcp_options *ao = &ipcp_allowoptions[f->unit];
 
-    wo->req_addr = (wo->neg_addr || wo->old_addrs) &&
-	(ao->neg_addr || ao->old_addrs);
+    wo->req_addr = ((wo->neg_addr || wo->old_addrs) &&
+	(ao->neg_addr || ao->old_addrs)) ||
+	(wo->hisaddr && !wo->accept_remote);
     if (wo->ouraddr == 0)
 	wo->accept_local = 1;
     if (wo->hisaddr == 0)
@@ -1648,7 +1649,8 @@ ipcp_reqci(fsm *f, u_char *inp,	int *len, int reject_if_disagree)
      * option safely.
      */
     if (rc != CONFREJ && !ho->neg_addr && !ho->old_addrs &&
-	wo->req_addr && !reject_if_disagree && !noremoteip) {
+	wo->req_addr && !reject_if_disagree &&
+	((wo->hisaddr && !wo->accept_remote) || !noremoteip)) {
 	if (rc == CONFACK) {
 	    rc = CONFNAK;
 	    ucp = inp;			/* reset pointer */