msc@qubix.UUCP (Mark Callow) (01/05/84)
Arrgh!! I've just spent a frustating hour trying to find out why binding to tcp port number 2048 failed with "permission denied" on a vax running 4.2 and worked on a Sun running 4.1c. It seems the port number specified in the 'struct sockaddr_in' must be in NETWORK order. This is the same as host order on a sun (68010) hence the program (which sun supplied) worked fine. On the vax it is byte and word swapped from host order so the program bombed when it tested the port against the reserved port numbers. (ie, was it < 1024?) I have not seen this *important* fact documented anywhere. I looked up the inet(4f) page and it doesn't say anything about the port address. It does say that "internet addresses are four byte quantities, stored in network standard format". This must be refering to the 'struct in_addr sin_addr' portion of the 'struct sockaddr_in' This seems an incredibly strange choice. Intuitively the user should be able to deal only with host order and leave it to the kernel to convert addresses as necessary. It is incredibly confusing to look up the constant IPPORT_RESERVED in /usr/include/netinet/in.h and find it has a value 1024 when a similar constant in your own program must be declared as 0x0004 or you must use htons(1024). Whoever wrote the code in the kernel that checks against IPPORT_RESERVED thought so too. {Her,His} comment was "GROSS". I was all set to change the kernel thinking it had to be a bug when I looked at the source for rlogind and for getservbyname and discovered that they byte swap port numbers. -- From the Tardis of Mark Callow msc@qubix.UUCP, decwrl!qubix!msc@Berkeley.ARPA ...{decvax,ucbvax,ihnp4}!decwrl!qubix!msc, ...{ittvax,amd70}!qubix!msc
jsq@ut-sally.UUCP (John Quarterman) (01/06/84)
x From: msc@qubix.UUCP (Mark Callow) Message-ID: <747@qubix.UUCP> Date: Wed, 4-Jan-84 15:46:36 CST ... It seems the port number specified in the 'struct sockaddr_in' must be in NETWORK order. This is the same as host order on a sun (68010) hence the program (which sun supplied) worked fine. On the vax it is byte and word swapped from host order so the program bombed when it tested the port against the reserved port numbers. (ie, was it < 1024?) I have not seen this *important* fact documented anywhere. I looked up the inet(4f) page and it doesn't say anything about the port address. It does say that "internet addresses are four byte quantities, stored in network standard format". This must be refering to the 'struct in_addr sin_addr' portion of the 'struct sockaddr_in' From byteorder(3n): DESCRIPTION These routines convert 16 and 32 bit quantities between net- work byte order and host byte order. On machines such as the SUN these routines are defined as null macros in the include file <_n_e_t_i_n_e_t/_i_n._h>. These routines are most often used in conjunction with Internet addresses and ports as returned by _g_e_t_h_o_s_t_e_n_t(3N) and _g_e_t_s_e_r_v_e_n_t(3N). SEE ALSO gethostent(3N), getservent(3N) BUGS The VAX handles bytes backwards from most everyone else in the world. This is not expected to be fixed in the near future. Seems pretty obvious to me from this that any 16 or 32 bit integer that goes out over the Internet must be byte swapped. Port numbers are 32 bits. Of course, the version of byteorder(3N) above came from a VAX, but I'd guess it's the same on SUN's 4.2. This seems an incredibly strange choice. Intuitively the user should be able to deal only with host order and leave it to the kernel to convert addresses as necessary. It is incredibly confusing to look up the constant IPPORT_RESERVED in /usr/include/netinet/in.h and find it has a value 1024 when a similar constant in your own program must be declared as 0x0004 or you must use htons(1024). Whoever wrote the code in the kernel that checks against IPPORT_RESERVED thought so too. {Her,His} comment was "GROSS". And I always thought the GROSS comment referred to the idea of reserving a range of port numbers that only root could listen on.... -- John Quarterman, CS Dept., University of Texas, Austin, Texas {ihnp4,seismo,ctvax}!ut-sally!jsq, jsq@ut-sally.{ARPA,UUCP}