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net-ipv6: add support for sockopt(SOL_IPV6, IPV6_FREEBIND)

PATCH Applied Maciej Żenczykowski 2 participants 2 messages Sep 27, 2017 – Sep 30, 2017

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Maciej Żenczykowski

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#0 lore raw

PATCH 1/1 net-ipv6: add support for sockopt(SOL_IPV6, IPV6_FREEBIND)

From: Maciej Żenczykowski <[email protected]>

So far we've been relying on sockopt(SOL_IP, IP_FREEBIND) being usable even on IPv6 sockets.

However, it turns out it is perfectly reasonable to want to set freebind on an AF_INET6 SOCK_RAW socket - but there is no way to set any SOL_IP socket option on such a socket (they're all blindly errored out).

One use case for this is to allow spoofing src ip on a raw socket via sendmsg cmsg.

Tested:
built, and booted

  # python
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import socket
SOL_IP = socket.SOL_IP
SOL_IPV6 = socket.IPPROTO_IPV6
IP_FREEBIND = 15
IPV6_FREEBIND = 78
s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, 0) s.getsockopt(SOL_IP, IP_FREEBIND)

0

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s.getsockopt(SOL_IPV6, IPV6_FREEBIND)

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s.setsockopt(SOL_IPV6, IPV6_FREEBIND, 1)
s.getsockopt(SOL_IP, IP_FREEBIND)

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s.getsockopt(SOL_IPV6, IPV6_FREEBIND)

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Signed-off-by Maciej Żenczykowski <[email protected]>
---
 include/uapi/linux/in6.h |  1 +
 net/ipv6/ipv6_sockglue.c | 12 ++++++++++++
 2 files changed, 13 insertions(+)
include/uapi/linux/in6.h +1 -0
index 46444f8fbee4..4f8f3eb0699f 100644
@@ -284,6 +284,7 @@ struct in6_flowlabel_req {
 #define IPV6_TRANSPARENT        75
 #define IPV6_UNICAST_IF         76
 #define IPV6_RECVFRAGSIZE	77
+#define IPV6_FREEBIND		78
 
 /*
  * Multicast Routing:
net/ipv6/ipv6_sockglue.c +12 -0
index a5e466d4e093..b9404feabd78 100644
@@ -377,6 +377,14 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 		retv = 0;
 		break;
 
+	case IPV6_FREEBIND:
+		if (optlen < sizeof(int))
+			goto e_inval;
+		/* we also don't have a separate freebind bit for IPV6 */
+		inet_sk(sk)->freebind = valbool;
+		retv = 0;
+		break;
+
 	case IPV6_RECVORIGDSTADDR:
 		if (optlen < sizeof(int))
 			goto e_inval;

@@ -1214,6 +1222,10 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		val = inet_sk(sk)->transparent;
 		break;
 
+	case IPV6_FREEBIND:
+		val = inet_sk(sk)->freebind;
+		break;
+
 	case IPV6_RECVORIGDSTADDR:
 		val = np->rxopt.bits.rxorigdstaddr;
 		break;
Signature · 1 line
2.14.1.992.g2c7b836f3a-goog
maintainer Applied
#1 lore raw

From: Maciej Żenczykowski <[email protected]>
Date: Tue, 26 Sep 2017 21:32:42 -0700

Quoted 24 lines

From: Maciej Żenczykowski <[email protected]>

So far we've been relying on sockopt(SOL_IP, IP_FREEBIND) being usable even on IPv6 sockets.

However, it turns out it is perfectly reasonable to want to set freebind on an AF_INET6 SOCK_RAW socket - but there is no way to set any SOL_IP socket option on such a socket (they're all blindly errored out).

One use case for this is to allow spoofing src ip on a raw socket via sendmsg cmsg.

Tested:
built, and booted

  # python
Quoted 7 lines
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import socket
SOL_IP = socket.SOL_IP
SOL_IPV6 = socket.IPPROTO_IPV6
IP_FREEBIND = 15
IPV6_FREEBIND = 78
s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, 0) s.getsockopt(SOL_IP, IP_FREEBIND)

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s.getsockopt(SOL_IPV6, IPV6_FREEBIND)

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s.setsockopt(SOL_IPV6, IPV6_FREEBIND, 1)
s.getsockopt(SOL_IP, IP_FREEBIND)

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s.getsockopt(SOL_IPV6, IPV6_FREEBIND)

1

Signed-off-by Maciej Żenczykowski <[email protected]>

Applied to net-next, thanks.