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ETH_MAC indirection erratum

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Pervasive misuse of "ETH_MAC *" (a pointer to an ETH_MAC, aka a 6
element unsigned char array) when a simple "ETH_MAC" is correct.  The
best example of this was eth_mac_fmt() in sim_ether.c with the following
prototype:

    t_stat eth_mac_fmt (ETH_MAC* const mac, char* strmac)

The first parameter is a pointer to an array of 6 unsigned characters,
whereas it really just wants to be a pointer to the first element of the
array:

    t_stat eth_mac_scan (const ETH_MAC mac, char* strmac)

The "ETH_MAC *" indirection error also results in subtle memcpy() and
memcmp() issues, e.g.:

    void network_func(DEVICE *dev, ETH_MAC *mac)
    {
      ETH_MAC other_mac;

      /* ...code... */

      /* memcpy() bug: */
      memcpy(other_mac, mac, sizeof(ETH_MAC));

      /* or worse: */
      memcpy(mac, other_mac, sizeof(ETH_MAC));
    }

eth_copy_mac() and eth_mac_cmp() replace calls to memcpy() and memcmp()
that copy or compare Ethernet MAC addresses. These are type-enforcing
functions, i.e., the parameters are ETH_MAC-s, to avoid the subtle
memcpy() and memcmp() bugs.

This fix solves at least one Heisenbug in _eth_close() while free()-ing
write request buffers (and possibly other Heisenbugs.)
This commit is contained in:
B. Scott Michel
2025-03-03 16:26:28 -08:00
committed by Paul Koning
parent 73e5df3928
commit c20b391eea
10 changed files with 256 additions and 225 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
3B2/3b2_ni.c
View File

@@ -557,7 +557,7 @@ t_stat ni_setmac(UNIT *uptr, int32 val, CONST char* cptr, void* desc)
UNUSED(desc);
status = SCPE_OK;
status = eth_mac_scan_ex(&ni.macs[NI_NIC_MAC], cptr, uptr);
status = eth_mac_scan_ex(ni.macs[NI_NIC_MAC], cptr, uptr);
if (status == SCPE_OK) {
eth_filter(ni.eth, ni.filter_count, ni.macs, 0, 0);
@@ -577,7 +577,7 @@ t_stat ni_showmac(FILE* st, UNIT* uptr, int32 val, CONST void* desc)
UNUSED(val);
UNUSED(desc);
eth_mac_fmt(&ni.macs[NI_NIC_MAC], buffer);
eth_mac_fmt(ni.macs[NI_NIC_MAC], buffer);
fprintf(st, "MAC=%s", buffer);
return SCPE_OK;
}
@@ -591,12 +591,12 @@ t_stat ni_show_filters(FILE* st, UNIT* uptr, int32 val, CONST void* desc)
UNUSED(val);
UNUSED(desc);
eth_mac_fmt(&ni.macs[NI_NIC_MAC], buffer);
eth_mac_fmt(ni.macs[NI_NIC_MAC], buffer);
fprintf(st, "Physical Address=%s\n", buffer);
if (ni.filter_count > 0) {
fprintf(st, "Filters:\n");
for (i=0; i < ni.filter_count; i++) {
eth_mac_fmt((ETH_MAC *) ni.macs[i], buffer);
eth_mac_fmt(ni.macs[i], buffer);
fprintf(st, "[%2d]: %s\n", i, buffer);
}
fprintf(st, "\n");
@@ -948,7 +948,7 @@ t_stat ni_attach(UNIT *uptr, CONST char *cptr)
return status;
}
status = eth_check_address_conflict(ni.eth, &ni.macs[NI_NIC_MAC]);
status = eth_check_address_conflict(ni.eth, ni.macs[NI_NIC_MAC]);
if (status != SCPE_OK) {
sim_debug(DBG_ERR, &ni_dev, "ni_attach failure: mac check\n");
eth_close(ni.eth);