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Preferred backend for TUN is UDP, not TCP

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Gerhard Rieger 2020-12-13 22:14:04 +01:00
parent cc3cd744d9
commit dabcc7f3d5
2 changed files with 13 additions and 6 deletions
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@ -186,6 +186,10 @@ Documentation:
Address UDP-RECV does not support option fork. Address UDP-RECV does not support option fork.
Thanks to Fulvio Scapin for reporting that mistake in docu. Thanks to Fulvio Scapin for reporting that mistake in docu.
TUN address documentation showed TCP for backend which may merge
consecutive packets which causes data loss.
Thanks to Tomasz Lakota for reporting this issue.
####################### V 1.7.3.4: ####################### V 1.7.3.4:
Corrections: Corrections:

13
doc/socat.yo
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@ -1048,6 +1048,9 @@ label(ADDRESS_TUN)dit(bf(tt(TUN[:<if-addr>/<bits>])))
requires read and write access to the tunnel cloning device, usually requires read and write access to the tunnel cloning device, usually
code(/dev/net/tun), as well as permission to set some tt(ioctl()s). code(/dev/net/tun), as well as permission to set some tt(ioctl()s).
bf(Option iff-up is required to immediately activate the interface!)nl() bf(Option iff-up is required to immediately activate the interface!)nl()
Note: If you intend to transfer packets between two Socat "wire sides" you
need a protocol that keeps packet boundaries, e.g.UDP; TCP might work with
option link(nodelay)(OPTION_TCP_NODELAY).nl()
Option groups: link(FD)(GROUP_FD),link(NAMED)(GROUP_NAMED),link(OPEN)(GROUP_OPEN),link(TUN)(GROUP_TUN) nl() Option groups: link(FD)(GROUP_FD),link(NAMED)(GROUP_NAMED),link(OPEN)(GROUP_OPEN),link(TUN)(GROUP_TUN) nl()
Useful options: Useful options:
link(iff-up)(OPTION_IFF_UP), link(iff-up)(OPTION_IFF_UP),
@ -2223,7 +2226,7 @@ label(GROUP_TCP)em(bf(TCP option group))
These options may be applied to TCP sockets. They work by invoking code(setsockopt()) with the appropriate parameters. These options may be applied to TCP sockets. They work by invoking code(setsockopt()) with the appropriate parameters.
startdit() startdit()
label(OPTION_CORK)dit(bf(tt(cork))) label(OPTION_TCP_CORK)dit(bf(tt(cork)))
Doesn't send packets smaller than MSS (maximal segment size). Doesn't send packets smaller than MSS (maximal segment size).
label(OPTION_DEFER-ACCEPT)dit(bf(tt(defer-accept))) label(OPTION_DEFER-ACCEPT)dit(bf(tt(defer-accept)))
While listening, accepts connections only when data from the peer arrived. While listening, accepts connections only when data from the peer arrived.
@ -2247,7 +2250,7 @@ label(OPTION_MSS)dit(bf(tt(mss=<bytes>)))
label(OPTION_MSS_LATE)dit(bf(tt(mss-late=<bytes>))) label(OPTION_MSS_LATE)dit(bf(tt(mss-late=<bytes>)))
Sets the MSS of the socket after connection has been established to <bytes> Sets the MSS of the socket after connection has been established to <bytes>
[link(int)(TYPE_INT)]. [link(int)(TYPE_INT)].
label(OPTION_NODELAY)dit(bf(tt(nodelay))) label(OPTION_TCP_NODELAY)dit(bf(tt(nodelay)))
Turns off the Nagle algorithm for measuring the RTT (round trip time). Turns off the Nagle algorithm for measuring the RTT (round trip time).
label(OPTION_RFC1323)dit(bf(tt(rfc1323))) label(OPTION_RFC1323)dit(bf(tt(rfc1323)))
Enables RFC1323 TCP options: TCP window scale, round-trip time measurement Enables RFC1323 TCP options: TCP window scale, round-trip time measurement
@ -3475,13 +3478,13 @@ operating system, bridges, or a badly configured switch.
label(EXAMPLE_ADDRESS_TUN) label(EXAMPLE_ADDRESS_TUN)
dit(bf(tt(socat TCP:host2:4443 TUN:192.168.255.1/24,up))) dit(bf(tt(socat UDP:host2:4443 TUN:192.168.255.1/24,up)))
establishes one side of a virtual (but not private!) network with host2 where a establishes one side of a virtual (but not private!) network with host2 where a
similar process might run, with UDP-L and tun address 192.168.255.2. They can similar process might run, with UDP-L and tun address 192.168.255.2. They can
reach each other using the addresses 192.168.255.1 and 192.168.255.2. Note that reach each other using the addresses 192.168.255.1 and 192.168.255.2. Note that
streaming eg. via TCP or SSL does not guarantee to retain packet boundaries and streaming eg.via TCP or SSL does not guarantee to retain packet boundaries and
may thus cause packet loss. might thus cause packet loss.
label(EXAMPLE_ADDRESS_VSOCK) label(EXAMPLE_ADDRESS_VSOCK)