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c61a2a76e5
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
115 lines
2.8 KiB
C
115 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef LINUX_MLD_H
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#define LINUX_MLD_H
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#include <linux/in6.h>
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#include <linux/icmpv6.h>
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/* MLDv1 Query/Report/Done */
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struct mld_msg {
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struct icmp6hdr mld_hdr;
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struct in6_addr mld_mca;
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};
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#define mld_type mld_hdr.icmp6_type
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#define mld_code mld_hdr.icmp6_code
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#define mld_cksum mld_hdr.icmp6_cksum
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#define mld_maxdelay mld_hdr.icmp6_maxdelay
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#define mld_reserved mld_hdr.icmp6_dataun.un_data16[1]
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/* Multicast Listener Discovery version 2 headers */
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/* MLDv2 Report */
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struct mld2_grec {
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__u8 grec_type;
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__u8 grec_auxwords;
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__be16 grec_nsrcs;
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struct in6_addr grec_mca;
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struct in6_addr grec_src[];
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};
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struct mld2_report {
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struct icmp6hdr mld2r_hdr;
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struct mld2_grec mld2r_grec[];
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};
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#define mld2r_type mld2r_hdr.icmp6_type
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#define mld2r_resv1 mld2r_hdr.icmp6_code
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#define mld2r_cksum mld2r_hdr.icmp6_cksum
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#define mld2r_resv2 mld2r_hdr.icmp6_dataun.un_data16[0]
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#define mld2r_ngrec mld2r_hdr.icmp6_dataun.un_data16[1]
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/* MLDv2 Query */
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struct mld2_query {
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struct icmp6hdr mld2q_hdr;
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struct in6_addr mld2q_mca;
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#if defined(__LITTLE_ENDIAN_BITFIELD)
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__u8 mld2q_qrv:3,
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mld2q_suppress:1,
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mld2q_resv2:4;
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#elif defined(__BIG_ENDIAN_BITFIELD)
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__u8 mld2q_resv2:4,
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mld2q_suppress:1,
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mld2q_qrv:3;
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#else
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#error "Please fix <asm/byteorder.h>"
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#endif
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__u8 mld2q_qqic;
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__be16 mld2q_nsrcs;
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struct in6_addr mld2q_srcs[];
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};
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#define mld2q_type mld2q_hdr.icmp6_type
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#define mld2q_code mld2q_hdr.icmp6_code
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#define mld2q_cksum mld2q_hdr.icmp6_cksum
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#define mld2q_mrc mld2q_hdr.icmp6_maxdelay
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#define mld2q_resv1 mld2q_hdr.icmp6_dataun.un_data16[1]
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/* RFC3810, 5.1.3. Maximum Response Code:
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*
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* If Maximum Response Code >= 32768, Maximum Response Code represents a
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* floating-point value as follows:
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*
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* 0 1 2 3 4 5 6 7 8 9 A B C D E F
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* |1| exp | mant |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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#define MLDV2_MRC_EXP(value) (((value) >> 12) & 0x0007)
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#define MLDV2_MRC_MAN(value) ((value) & 0x0fff)
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/* RFC3810, 5.1.9. QQIC (Querier's Query Interval Code):
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*
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* If QQIC >= 128, QQIC represents a floating-point value as follows:
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*
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* 0 1 2 3 4 5 6 7
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* +-+-+-+-+-+-+-+-+
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* |1| exp | mant |
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* +-+-+-+-+-+-+-+-+
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*/
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#define MLDV2_QQIC_EXP(value) (((value) >> 4) & 0x07)
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#define MLDV2_QQIC_MAN(value) ((value) & 0x0f)
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#define MLD_EXP_MIN_LIMIT 32768UL
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#define MLDV1_MRD_MAX_COMPAT (MLD_EXP_MIN_LIMIT - 1)
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static inline unsigned long mldv2_mrc(const struct mld2_query *mlh2)
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{
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/* RFC3810, 5.1.3. Maximum Response Code */
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unsigned long ret, mc_mrc = ntohs(mlh2->mld2q_mrc);
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if (mc_mrc < MLD_EXP_MIN_LIMIT) {
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ret = mc_mrc;
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} else {
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unsigned long mc_man, mc_exp;
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mc_exp = MLDV2_MRC_EXP(mc_mrc);
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mc_man = MLDV2_MRC_MAN(mc_mrc);
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ret = (mc_man | 0x1000) << (mc_exp + 3);
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}
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return ret;
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}
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#endif
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