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[lwip-devel] TCP source port numbers

From: Ullberg, Gustaf
Subject: [lwip-devel] TCP source port numbers
Date: Mon, 11 Apr 2011 13:31:42 +0200


I have a problem with some networks dropping my "TCP SYN" packets. It seems like the networks drop packets with certain source port numbers.

The range of the source port numbers are defined in lwip/src/core/tcp.c:
#define TCP_LOCAL_PORT_RANGE_END   0x7fff

According to the Internet Assigned Numbers Authority (IANA), these port numbers should not be used as they lie in the range of "registered ports".

Excerpt from http://www.iana.org/assignments/port-numbers :
"The Registered Ports are those from 1024 through 49151
DCCP Registered ports SHOULD NOT be used without IANA registration.
The registration procedure is defined in [RFC4340], Section 19.9.
The Dynamic and/or Private Ports are those from 49152 through 65535"

To avoid that others are affected by this problem, I suggest that we change the macros to:
#define TCP_LOCAL_PORT_RANGE_START 0xc000 // 49152
#define TCP_LOCAL_PORT_RANGE_END   0xffff // 65535

Best regards

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