Re: sendmsg(2) with IP_PKTINFO

[Ryo Shimizu <ryo%nerv.org@localhost>]

>>>
>>> +				/* Checking laddr:port already in use? */
>>> +				xinp = in_pcblookup_bind(&udbtable,
>>> +				    laddr.sin_addr, inp->inp_lport);
>>> +				if ((xinp != NULL) && (xinp != inp)) {
>>> +					error = EADDRINUSE;
>>> +					goto release;
>>> +				}
>>> +				break;
>>>
>>> Why is this check needed and why is it UDP specific?
>>>
>>> In dhcpcd's case it's already bound the local address the socket and the
>>> kernel then claims the address is already in use which is wrong.
>> 
>> I thought that it should fail with EADDRINUSE if sendmsg with IP_PKTINFO
>> using address:port same as already bound on other socket.
>> 
>> Certainly, this behavior is different from IP6_PKTINFO and linux.
>> Should I fix to be able to PKTINFO with address:port that another socket bound?
>
>Yes please!
>
>Consider this use case:
>https://roy.marples.name/git/dhcpcd.git/tree/src/dhcp.c#n1687
>I am only using IP_PKTINFO to set the outbound interface, not influence 
>any address.
>
>As things stand the kernel check noted above returns EADDRINUSE.
>If I either remove the kernel check OR disable IP_PKTINFO in dhcpcd then 
>the message is sent.
>
>To make the code easier to read, I bind to the unspecified 
>address:BOOTPC so that ICMP unreachable messages are not sent by the 
>kernel during DHCP init. This socket is kept open for the lifetime of 
>dhcpcd and just drained down.
>
>When dhcpcd needs to unicast to the DHCP server, it opens another 
>socket, binds DHCPADDRESS:BOOTPC and then sends. This works fine without 
>IP_PKTINFO and I would like to use IP_PKTINFO just to force the outbound 
>interface. We're not actively listening on this socket, just sending. My 
>expectation is that this should work.
>
>Can you fix this please?

Ok, Please try this patch. If no problem for dhcpcd, I'll commit.

cvs -q diff -aup .
Index: ip_output.c
===================================================================
RCS file: /src/cvs/cvsroot-netbsd/src/sys/netinet/ip_output.c,v
retrieving revision 1.285
diff -a -u -p -r1.285 ip_output.c
--- ip_output.c	17 Nov 2017 07:37:12 -0000	1.285
+++ ip_output.c	8 Dec 2017 16:59:52 -0000
@@ -1411,9 +1411,8 @@ ip_pktinfo_prepare(const struct in_pktin
  */
 int
 ip_setpktopts(struct mbuf *control, struct ip_pktopts *pktopts, int *flags,
-    struct inpcb *inp, kauth_cred_t cred, int uproto)
+    struct inpcb *inp, kauth_cred_t cred)
 {
-	struct inpcb *xinp;
 	struct cmsghdr *cm;
 	struct in_pktinfo *pktinfo;
 	int error;
@@ -1453,16 +1452,6 @@ ip_setpktopts(struct mbuf *control, stru
 			    cred);
 			if (error != 0)
 				return error;
-
-			if ((uproto == IPPROTO_UDP) &&
-			    !in_nullhost(pktopts->ippo_laddr.sin_addr)) {
-				/* Checking laddr:port already in use? */
-				xinp = in_pcblookup_bind(&udbtable,
-				    pktopts->ippo_laddr.sin_addr,
-				    inp->inp_lport);
-				if ((xinp != NULL) && (xinp != inp))
-					return EADDRINUSE;
-			}
 			break;
 		default:
 			return ENOPROTOOPT;
Index: ip_var.h
===================================================================
RCS file: /src/cvs/cvsroot-netbsd/src/sys/netinet/ip_var.h,v
retrieving revision 1.120
diff -a -u -p -r1.120 ip_var.h
--- ip_var.h	10 Aug 2017 04:31:58 -0000	1.120
+++ ip_var.h	8 Dec 2017 17:00:03 -0000
@@ -215,7 +215,7 @@ void	in_init(void);
 
 int	 ip_ctloutput(int, struct socket *, struct sockopt *);
 int	 ip_setpktopts(struct mbuf *, struct ip_pktopts *, int *,
-	    struct inpcb *, kauth_cred_t, int);
+	    struct inpcb *, kauth_cred_t);
 void	 ip_drain(void);
 void	 ip_drainstub(void);
 void	 ip_freemoptions(struct ip_moptions *);
Index: raw_ip.c
===================================================================
RCS file: /src/cvs/cvsroot-netbsd/src/sys/netinet/raw_ip.c,v
retrieving revision 1.166
diff -a -u -p -r1.166 raw_ip.c
--- raw_ip.c	10 Aug 2017 04:31:58 -0000	1.166
+++ raw_ip.c	8 Dec 2017 17:00:08 -0000
@@ -322,8 +322,7 @@ rip_output(struct mbuf *m, struct inpcb 
 
 	/* Setup IP outgoing packet options */
 	memset(&pktopts, 0, sizeof(pktopts));
-	error = ip_setpktopts(control, &pktopts, &flags, inp, cred,
-	    IPPROTO_RAW);
+	error = ip_setpktopts(control, &pktopts, &flags, inp, cred);
 	if (control != NULL)
 		m_freem(control);
 	if (error != 0)
Index: udp_usrreq.c
===================================================================
RCS file: /src/cvs/cvsroot-netbsd/src/sys/netinet/udp_usrreq.c,v
retrieving revision 1.235
diff -a -u -p -r1.235 udp_usrreq.c
--- udp_usrreq.c	10 Aug 2017 04:31:58 -0000	1.235
+++ udp_usrreq.c	8 Dec 2017 17:00:19 -0000
@@ -804,8 +804,7 @@ udp_output(struct mbuf *m, struct inpcb 
 
 	/* Setup IP outgoing packet options */
 	memset(&pktopts, 0, sizeof(pktopts));
-	error = ip_setpktopts(control, &pktopts, &flags, inp, cred,
-	    IPPROTO_UDP);
+	error = ip_setpktopts(control, &pktopts, &flags, inp, cred);
 	if (error != 0)
 		goto release;
 

--
ryo shimizu