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sockopt: add IP_DONTFRAG/IP_MTU_DISCOVER option #603

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Merged
merged 1 commit into from
Aug 5, 2025
+25 −2
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sockopt: add IP_DONTFRAG/IP_MTU_DISCOVER option #603

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1 change: 1 addition & 0 deletions Network/Socket.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -167,6 +167,7 @@ module Network.Socket (
RecvIPv4TTL,
RecvIPv4TOS,
RecvIPv4PktInfo,
DontFragment,
RecvIPv6HopLimit,
RecvIPv6TClass,
RecvIPv6PktInfo
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12 changes: 11 additions & 1 deletion Network/Socket/Options.hsc
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Expand Up @@ -16,7 +16,7 @@ module Network.Socket.Options (
,OOBInline,TimeToLive,MaxSegment,NoDelay,Cork,Linger,ReusePort
,RecvLowWater,SendLowWater,RecvTimeOut,SendTimeOut
,UseLoopBack,UserTimeout,IPv6Only
,RecvIPv4TTL,RecvIPv4TOS,RecvIPv4PktInfo
,RecvIPv4TTL,RecvIPv4TOS,RecvIPv4PktInfo,DontFragment
,RecvIPv6HopLimit,RecvIPv6TClass,RecvIPv6PktInfo
,CustomSockOpt)
, isSupportedSocketOption
Expand Down Expand Up @@ -94,6 +94,7 @@ socketOptionBijection =
, (RecvIPv4TTL, "RecvIPv4TTL")
, (RecvIPv4TOS, "RecvIPv4TOS")
, (RecvIPv4PktInfo, "RecvIPv4PktInfo")
, (DontFragment, "DontFragment")
, (IPv6Only, "IPv6Only")
, (RecvIPv6HopLimit, "RecvIPv6HopLimit")
, (RecvIPv6TClass, "RecvIPv6TClass")
Expand Down Expand Up @@ -352,6 +353,15 @@ pattern RecvIPv4PktInfo = SockOpt (#const IPPROTO_IP) (#const IP_PKTINFO)
#else
pattern RecvIPv4PktInfo = SockOpt (-1) (-1)
#endif
-- | IP_DONTFRAG
pattern DontFragment :: SocketOption
#if HAVE_DECL_IP_DONTFRAG
pattern DontFragment = SockOpt (#const IPPROTO_IP) (#const IP_DONTFRAG)
#elif HAVE_DECL_IP_MTU_DISCOVER
pattern DontFragment = SockOpt (#const IPPROTO_IP) (#const IP_MTU_DISCOVER)
#else
pattern DontFragment = SockOpt (-1) (-1)
#endif
#endif // HAVE_DECL_IPPROTO_IP

#if HAVE_DECL_IPPROTO_IPV6
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10 changes: 10 additions & 0 deletions Network/Socket/Syscall.hs
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Expand Up @@ -83,6 +83,7 @@ socket family stype protocol = E.bracketOnError create c_close $ \fd -> do
-- This socket is not managed by the IO manager yet.
-- So, we don't have to call "close" which uses "closeFdWith".
unsetIPv6Only s
setDontFragment s
return s
where
create = do
Expand Down Expand Up @@ -120,6 +121,15 @@ socket family stype protocol = E.bracketOnError create c_close $ \fd -> do
unsetIPv6Only _ = return ()
#endif

setDontFragment s = when (family == AF_INET) $
#if HAVE_DECL_IP_DONTFRAG || HAVE_DECL_IP_MTU_DISCOVER
setSocketOption s DontFragment 1
#else
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These four lines (#else clause) are not necessary

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@thehajime thehajime Aug 5, 2025 •
edited
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if there are OSs/kernels which don't have those sockoption, I guess the compilation fails like below.

Network/Socket/Syscall.hs:138:1: error: [GHC-58481]
    parse error (possibly incorrect indentation or mismatched brackets)
    |
138 | bind :: SocketAddress sa => Socket -> sa -> IO ()
    | ^

I followed the way ipv6only option does in the #else clause to work around this situation.
do you still think it's unnecessary ?

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Never mind.
I misunderstand that you are using setDontFragment here but you are defining it here.

-- do nothing
return ()
#endif


-----------------------------------------------------------------------------
-- Binding a socket

Expand Down
2 changes: 2 additions & 0 deletions configure.ac
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Expand Up @@ -86,6 +86,8 @@ AC_CHECK_DECLS([AI_ADDRCONFIG, AI_ALL, AI_NUMERICSERV, AI_V4MAPPED])
AC_CHECK_DECLS([IPV6_V6ONLY])
AC_CHECK_DECLS([IPPROTO_IP, IPPROTO_TCP, IPPROTO_IPV6])
AC_CHECK_DECLS([SO_PEERCRED])
AC_CHECK_DECLS([IP_DONTFRAG])
AC_CHECK_DECLS([IP_MTU_DISCOVER])

AC_CHECK_MEMBERS([struct msghdr.msg_control, struct msghdr.msg_accrights])
AC_CHECK_MEMBERS([struct sockaddr.sa_len])
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2 changes: 1 addition & 1 deletion tests/Network/SocketSpec.hs
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Expand Up @@ -460,7 +460,7 @@ sockoptPatterns = nub
,TimeToLive,MaxSegment,NoDelay,Cork,Linger,ReusePort
,RecvLowWater,SendLowWater,RecvTimeOut,SendTimeOut
,UseLoopBack,UserTimeout,IPv6Only
,RecvIPv4TTL,RecvIPv4TOS,RecvIPv4PktInfo
,RecvIPv4TTL,RecvIPv4TOS,RecvIPv4PktInfo,DontFragment
,RecvIPv6HopLimit,RecvIPv6TClass,RecvIPv6PktInfo]

cmsgidPatterns :: [CmsgId]
Expand Down