From 7c559a9e44ee61faf2f339604ce708decb345a93 Mon Sep 17 00:00:00 2001
From: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Date: Thu, 4 Oct 2007 14:39:22 -0700
Subject: [DCCP]: Add socket option to query the current MPS
This enables applications to query the current value of the Maximum
Packet Size via a socket option, suggested as a SHOULD in (RFC 4340,
p. 102).
This socket option is useful to avoid the annoying bail-out via
`-EMSGSIZE'. In particular, as fragmentation is not currently
supported (and its use is partly discouraged in RFC 4340).
With this option, it is possible to size buffers accordingly, e.g.
int buflen = dccp_get_cur_mps(sockfd);
/* or */
if (msgsize > dccp_get_cur_mps(sockfd))
die("message is too large for this path");
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/dccp/proto.c | 4 ++++
1 file changed, 4 insertions(+)
(limited to 'net')
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 7e4f54a4ec..c0b685efe2 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -587,6 +587,10 @@ static int do_dccp_getsockopt(struct sock *sk, int level, int optname,
case DCCP_SOCKOPT_SERVICE:
return dccp_getsockopt_service(sk, len,
(__be32 __user *)optval, optlen);
+ case DCCP_SOCKOPT_GET_CUR_MPS:
+ val = dp->dccps_mss_cache;
+ len = sizeof(val);
+ break;
case DCCP_SOCKOPT_SEND_CSCOV:
val = dp->dccps_pcslen;
len = sizeof(val);
--
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