From: Ben Greear <greearb@candelatech.com> Date: Sun, 12 Aug 2001 20:25:36 -0700 It appears that the IP TOS values in netinet/ip.h are incorrect: I'll be using the page you even quoted: http://www.hut.fi/~msisomak/diffserv.html to show that the values are correct. This page, in figure 2, shows the following bit layout: ---------------------------------------- | Precedence | Type of Service | 0 | ---------------------------------------- 8 7 6 5 4 3 2 1 0 The bit numbering above is mine, the page labels them backwards for whatever reason. #define IPTOS_TOS_MASK 0x1E #define IPTOS_TOS(tos) ((tos) & IPTOS_TOS_MASK) TOS field, bits 1 thru 5 #define IPTOS_LOWDELAY 0x10 Minimize delay, binary 1000 in TOS field. #define IPTOS_THROUGHPUT 0x08 Minimize thruput, binary 0100 in TOS field. #define IPTOS_RELIABILITY 0x04 Maximize reliability, binary 0010 in TOS field. #define IPTOS_LOWCOST 0x02 #define IPTOS_MINCOST IPTOS_LOWCOST Minimize monetary (misspelled on page) cost, binary 0001 in TOS field. Am I missing something?? I think the mislabelled bit numbering in the figure of that web page has mislead your thinking, that's all. At least, Linux and BSD's header files agree perfectly for these values :-) Also, will the kernel take any 8-bit value I try to stuff in there with: setsockopt(dev_socket, SOL_IP, IP_TOS, (char*)&val, sizeof(int)) or will it normalize values according to it's internal rules? 1) If you have any bits outside of the precidence or type of service field set, you will get -EINVAL. (basically if the lowest bit is set, it is reserved and thus invalid to pass to this sockopt) 2) If this is a TCP connection, and CONFIG_INET_ECN is enabled, the low two bits you pass will be replaced with the current ECN bit settings. The lowest two TOS byte bits are used for ECN. 3) If the precidence in the TOS value passed is greater than or equal to IPTOS_PREC_CRITIC_ECP, and the user does not uave CAP_NET_ADMIN capabilities, you will get an -EPERM failure. Basically, I just read aloud the code in net/ipv4/ip_sockglue.c which you could have just as easily have done by grepping for IPTOS under net/ipv4/*.c But I'll let you be lazy just this one time :-) Later, David S. Miller davem@redhat.com - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
