NetLabel: cleanup and document CIPSO constants
This patch collects all of the CIPSO constants and puts them in one place; it also documents each value explaining how the value is derived. Signed-off-by: Paul Moore <paul.moore@hp.com> Signed-off-by: James Morris <jmorris@namei.org>
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@ -91,6 +91,33 @@ static struct cipso_v4_map_cache_bkt *cipso_v4_cache = NULL;
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int cipso_v4_rbm_optfmt = 0;
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int cipso_v4_rbm_strictvalid = 1;
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/*
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* Protocol Constants
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*/
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/* Maximum size of the CIPSO IP option, derived from the fact that the maximum
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* IPv4 header size is 60 bytes and the base IPv4 header is 20 bytes long. */
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#define CIPSO_V4_OPT_LEN_MAX 40
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/* Length of the base CIPSO option, this includes the option type (1 byte), the
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* option length (1 byte), and the DOI (4 bytes). */
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#define CIPSO_V4_HDR_LEN 6
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/* Base length of the restrictive category bitmap tag (tag #1). */
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#define CIPSO_V4_TAG_RBM_BLEN 4
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/* Base length of the enumerated category tag (tag #2). */
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#define CIPSO_V4_TAG_ENUM_BLEN 4
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/* Base length of the ranged categories bitmap tag (tag #5). */
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#define CIPSO_V4_TAG_RNG_BLEN 4
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/* The maximum number of category ranges permitted in the ranged category tag
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* (tag #5). You may note that the IETF draft states that the maximum number
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* of category ranges is 7, but if the low end of the last category range is
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* zero then it is possibile to fit 8 category ranges because the zero should
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* be omitted. */
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#define CIPSO_V4_TAG_RNG_CAT_MAX 8
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/*
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* Helper Functions
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*/
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@ -1109,15 +1136,12 @@ static int cipso_v4_map_cat_rng_hton(const struct cipso_v4_doi *doi_def,
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unsigned char *net_cat,
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u32 net_cat_len)
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{
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/* The constant '16' is not random, it is the maximum number of
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* high/low category range pairs as permitted by the CIPSO draft based
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* on a maximum IPv4 header length of 60 bytes - the BUG_ON() assertion
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* does a sanity check to make sure we don't overflow the array. */
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int iter = -1;
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u16 array[16];
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u16 array[CIPSO_V4_TAG_RNG_CAT_MAX * 2];
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u32 array_cnt = 0;
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u32 cat_size = 0;
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/* make sure we don't overflow the 'array[]' variable */
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BUG_ON(net_cat_len > 30);
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for (;;) {
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@ -1196,9 +1220,6 @@ static int cipso_v4_map_cat_rng_ntoh(const struct cipso_v4_doi *doi_def,
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* Protocol Handling Functions
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*/
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#define CIPSO_V4_OPT_LEN_MAX 40
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#define CIPSO_V4_HDR_LEN 6
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/**
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* cipso_v4_gentag_hdr - Generate a CIPSO option header
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* @doi_def: the DOI definition
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