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ffaa906cd1bccc1eff1c263ec83d305cdb49f92f
DroidDeck/tools/linuxfs/preload/netif.c
T
Kurt Himebauch ffaa906cd1 fix: catch KGSL GEM_CLOSE at ioctl instead of exporting drmIoctl (#305) 
* fix: avoid reusing retired KGSL GEM handles

* fix: defer closing GEM_CLOSE'd KGSL dma-buf descriptors

* Revert "fix: defer closing GEM_CLOSE'd KGSL dma-buf descriptors"

This reverts commit 191bf4b6f2.

* test: interpose drmIoctl without releasing GEM_CLOSE handles

* fix: catch KGSL GEM_CLOSE at ioctl instead of exporting drmIoctl
2026-10-06 11:52:16 -04:00

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/*
* Ported from WinNative (maxjivi05, feature/wayland-gamescope, 2026-09-18/19), GPL-3.0, with names
* changed to this project's. The reasoning below is the original author's.
*
* Network interfaces for a sandbox that hides them.
*
* Android denies an app the rtnetlink dump behind getifaddrs() and if_nameindex(), the hardware
* address ioctl, and every table under /proc/net. Wine builds its adapter, address, route and
* neighbour tables from exactly those, so a game saw a machine with no adapter, no address, no
* gateway and no MAC, and one that checks its adapters before going online waited for good.
* The app knows the real link from ConnectivityManager and writes it to /etc/droiddeck-net;
* whatever the kernel refuses is answered from that file. Anything the kernel does answer wins.
*/
#define _GNU_SOURCE 1
#include <arpa/inet.h>
#include <dlfcn.h>
#include <errno.h>
#include <fcntl.h>
#include <ifaddrs.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <netpacket/packet.h>
#include <netinet/in.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <unistd.h>
#define LINK_FILE "/etc/droiddeck-net"
#define LO_NAME "lo"
#define LO_INDEX 1
#define LO_MTU 65536
#define MAX_ADDRS 16
struct link_addr {
int family;
unsigned char bytes[16];
unsigned prefix;
};
struct link {
char name[IFNAMSIZ];
unsigned index;
int mtu;
unsigned char mac[6];
struct link_addr addrs[MAX_ADDRS];
int addr_count;
struct link_addr gateways[2];
int gateway_count;
};
static int parse_addr(const char *text, struct link_addr *out) {
memset(out, 0, sizeof(*out));
if (inet_pton(AF_INET, text, out->bytes) == 1) out->family = AF_INET;
else if (inet_pton(AF_INET6, text, out->bytes) == 1) out->family = AF_INET6;
else return 0;
return 1;
}
/* Read on every call: the app rewrites the file when the device changes network. */
static int load_link(struct link *link) {
typedef FILE *(*fopen_fn)(const char *, const char *);
fopen_fn real_fopen = (fopen_fn) dlsym(RTLD_NEXT, "fopen");
FILE *f = real_fopen ? real_fopen(LINK_FILE, "re") : NULL;
if (f == NULL) return 0;
memset(link, 0, sizeof(*link));
char line[160], text[64];
unsigned m[6], prefix;
while (fgets(line, sizeof(line), f)) {
if (sscanf(line, "if %15s %u %d", link->name, &link->index, &link->mtu) == 3) continue;
if (sscanf(line, "mac %2x:%2x:%2x:%2x:%2x:%2x", m, m + 1, m + 2, m + 3, m + 4, m + 5) == 6) {
for (int i = 0; i < 6; i++) link->mac[i] = (unsigned char) m[i];
} else if (sscanf(line, "addr %63s %u", text, &prefix) == 2) {
struct link_addr addr;
if (link->addr_count < MAX_ADDRS && parse_addr(text, &addr)
&& prefix <= (addr.family == AF_INET ? 32u : 128u)) {
addr.prefix = prefix;
link->addrs[link->addr_count++] = addr;
}
} else if (sscanf(line, "gw %63s", text) == 1) {
struct link_addr addr;
if (link->gateway_count < 2 && parse_addr(text, &addr)) {
link->gateways[link->gateway_count++] = addr;
}
}
}
fclose(f);
return link->name[0] != '\0' && link->index > LO_INDEX && link->addr_count > 0;
}
static void prefix_mask(int family, unsigned prefix, unsigned char *out) {
int len = family == AF_INET ? 4 : 16;
for (int i = 0; i < len; i++, prefix -= prefix < 8 ? prefix : 8) {
out[i] = prefix >= 8 ? 0xff : (unsigned char) (0xff00 >> prefix);
}
}
static int is_link_local(const struct link_addr *addr) {
return addr->family == AF_INET6 && addr->bytes[0] == 0xfe && (addr->bytes[1] & 0xc0) == 0x80;
}
/* One allocation per list. ifa_data of the head points at the head itself, which glibc never
* does, so freeifaddrs() can tell the two kinds of list apart without keeping any state. */
struct entry {
struct ifaddrs ifa;
struct sockaddr_storage addr, mask, extra;
char name[IFNAMSIZ];
};
static struct entry *fill_entry(struct entry *e, const char *name, unsigned flags) {
snprintf(e->name, sizeof(e->name), "%s", name);
e->ifa.ifa_name = e->name;
e->ifa.ifa_flags = flags;
e->ifa.ifa_addr = (struct sockaddr *) &e->addr;
e[-1].ifa.ifa_next = &e->ifa;
return e;
}
static void fill_packet(struct entry *e, unsigned index, const unsigned char *mac) {
struct sockaddr_ll *ll = (struct sockaddr_ll *) &e->addr;
ll->sll_family = AF_PACKET;
ll->sll_ifindex = (int) index;
ll->sll_hatype = mac ? ARPHRD_ETHER : ARPHRD_LOOPBACK;
ll->sll_halen = 6;
if (mac) memcpy(ll->sll_addr, mac, 6);
}
static void fill_inet(struct entry *e, const struct link_addr *addr, unsigned index) {
unsigned char mask[16];
prefix_mask(addr->family, addr->prefix, mask);
e->ifa.ifa_netmask = (struct sockaddr *) &e->mask;
if (addr->family == AF_INET) {
struct sockaddr_in *sin = (struct sockaddr_in *) &e->addr;
struct sockaddr_in *smask = (struct sockaddr_in *) &e->mask;
sin->sin_family = smask->sin_family = AF_INET;
memcpy(&sin->sin_addr, addr->bytes, 4);
memcpy(&smask->sin_addr, mask, 4);
if (e->ifa.ifa_flags & IFF_BROADCAST) {
struct sockaddr_in *bcast = (struct sockaddr_in *) &e->extra;
bcast->sin_family = AF_INET;
bcast->sin_addr.s_addr = sin->sin_addr.s_addr | ~smask->sin_addr.s_addr;
e->ifa.ifa_broadaddr = (struct sockaddr *) bcast;
}
} else {
struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) &e->addr;
struct sockaddr_in6 *smask = (struct sockaddr_in6 *) &e->mask;
sin6->sin6_family = smask->sin6_family = AF_INET6;
memcpy(&sin6->sin6_addr, addr->bytes, 16);
memcpy(&smask->sin6_addr, mask, 16);
if (is_link_local(addr)) sin6->sin6_scope_id = index;
}
}
static const struct link_addr LO_V4 = { AF_INET, { 127, 0, 0, 1 }, 8 };
static const struct link_addr LO_V6 = { AF_INET6, { [15] = 1 }, 128 };
static int real_list_usable(const struct ifaddrs *list) {
for (const struct ifaddrs *e = list; e; e = e->ifa_next) {
if (e->ifa_addr && e->ifa_addr->sa_family == AF_INET && !(e->ifa_flags & IFF_LOOPBACK)) {
return 1;
}
}
return 0;
}
int getifaddrs(struct ifaddrs **out) {
typedef int (*getifaddrs_fn)(struct ifaddrs **);
typedef void (*freeifaddrs_fn)(struct ifaddrs *);
getifaddrs_fn real = (getifaddrs_fn) dlsym(RTLD_NEXT, "getifaddrs");
struct ifaddrs *list = NULL;
int rc = real(&list);
int saved = errno;
if (rc == 0 && real_list_usable(list)) {
*out = list;
return 0;
}
struct link link;
if (!load_link(&link)) {
if (rc == 0) *out = list;
errno = saved;
return rc;
}
if (rc == 0 && list) ((freeifaddrs_fn) dlsym(RTLD_NEXT, "freeifaddrs"))(list);
/* A leading slot keeps fill_entry()'s back link in bounds; the list starts after it. */
struct entry *block = calloc((size_t) link.addr_count + 5, sizeof(*block));
if (block == NULL) {
errno = ENOMEM;
return -1;
}
unsigned lo_flags = IFF_UP | IFF_RUNNING | IFF_LOOPBACK;
unsigned up_flags = IFF_UP | IFF_RUNNING | IFF_BROADCAST | IFF_MULTICAST;
struct entry *e = block;
fill_packet(fill_entry(++e, LO_NAME, lo_flags), LO_INDEX, NULL);
fill_inet(fill_entry(++e, LO_NAME, lo_flags), &LO_V4, LO_INDEX);
fill_inet(fill_entry(++e, LO_NAME, lo_flags), &LO_V6, LO_INDEX);
fill_packet(fill_entry(++e, link.name, up_flags), link.index, link.mac);
for (int i = 0; i < link.addr_count; i++) {
fill_inet(fill_entry(++e, link.name, up_flags), &link.addrs[i], link.index);
}
block[1].ifa.ifa_data = &block[1].ifa;
*out = &block[1].ifa;
return 0;
}
void freeifaddrs(struct ifaddrs *list) {
typedef void (*freeifaddrs_fn)(struct ifaddrs *);
if (list == NULL) return;
if (list->ifa_data == list) {
free((struct entry *) list - 1);
return;
}
((freeifaddrs_fn) dlsym(RTLD_NEXT, "freeifaddrs"))(list);
}
/* Names live in the same allocation as the array, right behind it; glibc strdup()s each one. */
struct name_block {
struct if_nameindex index[3];
char names[2][IFNAMSIZ];
};
struct if_nameindex *if_nameindex(void) {
typedef struct if_nameindex *(*if_nameindex_fn)(void);
struct if_nameindex *list = ((if_nameindex_fn) dlsym(RTLD_NEXT, "if_nameindex"))();
int saved = errno;
if (list && list[0].if_index != 0) return list;
struct link link;
struct name_block *block;
if (!load_link(&link) || (block = calloc(1, sizeof(*block))) == NULL) {
errno = saved;
return list;
}
if (list) if_freenameindex(list);
snprintf(block->names[0], IFNAMSIZ, "%s", LO_NAME);
snprintf(block->names[1], IFNAMSIZ, "%s", link.name);
block->index[0] = (struct if_nameindex) { LO_INDEX, block->names[0] };
block->index[1] = (struct if_nameindex) { link.index, block->names[1] };
return block->index;
}
void if_freenameindex(struct if_nameindex *list) {
typedef void (*if_freenameindex_fn)(struct if_nameindex *);
if (list == NULL) return;
if (list[0].if_name == ((struct name_block *) list)->names[0]) {
free(list);
return;
}
((if_freenameindex_fn) dlsym(RTLD_NEXT, "if_freenameindex"))(list);
}
unsigned int if_nametoindex(const char *name) {
typedef unsigned int (*if_nametoindex_fn)(const char *);
unsigned int index = ((if_nametoindex_fn) dlsym(RTLD_NEXT, "if_nametoindex"))(name);
if (index != 0 || name == NULL) return index;
int saved = errno;
struct link link;
if (strcmp(name, LO_NAME) == 0) return LO_INDEX;
if (load_link(&link) && strcmp(name, link.name) == 0) return link.index;
errno = saved;
return 0;
}
char *if_indextoname(unsigned int index, char name[IF_NAMESIZE]) {
typedef char *(*if_indextoname_fn)(unsigned int, char *);
char *found = ((if_indextoname_fn) dlsym(RTLD_NEXT, "if_indextoname"))(index, name);
if (found || name == NULL) return found;
int saved = errno;
struct link link;
if (index == LO_INDEX) return strcpy(name, LO_NAME);
if (load_link(&link) && index == link.index) return strcpy(name, link.name);
errno = saved;
return NULL;
}
static int mac_unusable(const struct ifreq *ifr) {
const unsigned char *a = (const unsigned char *) ifr->ifr_hwaddr.sa_data;
if (ifr->ifr_hwaddr.sa_family != ARPHRD_ETHER) return 1;
/* Android hands out 02:00:00:00:00:00 where it hides the real address. */
int rest = a[1] | a[2] | a[3] | a[4] | a[5];
return (a[0] & 0x03) || (rest == 0 && (a[0] == 0 || a[0] == 0x02));
}
static const struct link_addr *first_v4(const struct link *link) {
for (int i = 0; i < link->addr_count; i++) {
if (link->addrs[i].family == AF_INET) return &link->addrs[i];
}
return NULL;
}
static int answer_ifreq(unsigned long request, struct ifreq *ifr, int real_rc) {
char name[IFNAMSIZ + 1] = { 0 };
memcpy(name, ifr->ifr_name, IFNAMSIZ);
int loopback = strcmp(name, LO_NAME) == 0;
struct link link;
if (!load_link(&link) || (!loopback && strcmp(name, link.name) != 0)) return 0;
if (request == SIOCGIFHWADDR) {
if (real_rc == 0 && (loopback || !mac_unusable(ifr))) return 0;
memset(&ifr->ifr_hwaddr, 0, sizeof(ifr->ifr_hwaddr));
ifr->ifr_hwaddr.sa_family = loopback ? ARPHRD_LOOPBACK : ARPHRD_ETHER;
if (!loopback) memcpy(ifr->ifr_hwaddr.sa_data, link.mac, 6);
return 1;
}
if (real_rc == 0) return 0;
const struct link_addr *v4 = loopback ? &LO_V4 : first_v4(&link);
struct sockaddr_in *sin = (struct sockaddr_in *) &ifr->ifr_addr;
unsigned char mask[16];
switch (request) {
case SIOCGIFFLAGS:
ifr->ifr_flags = loopback ? IFF_UP | IFF_RUNNING | IFF_LOOPBACK
: IFF_UP | IFF_RUNNING | IFF_BROADCAST | IFF_MULTICAST;
return 1;
case SIOCGIFMTU:
ifr->ifr_mtu = loopback ? LO_MTU : link.mtu;
return 1;
case SIOCGIFINDEX:
ifr->ifr_ifindex = loopback ? LO_INDEX : (int) link.index;
return 1;
case SIOCGIFADDR:
case SIOCGIFNETMASK:
case SIOCGIFBRDADDR:
if (v4 == NULL) return 0;
prefix_mask(AF_INET, v4->prefix, mask);
memset(sin, 0, sizeof(*sin));
sin->sin_family = AF_INET;
for (int i = 0; i < 4; i++) {
unsigned char *out = (unsigned char *) &sin->sin_addr + i;
*out = request == SIOCGIFNETMASK ? mask[i]
: request == SIOCGIFADDR ? v4->bytes[i]
: (unsigned char) (v4->bytes[i] | ~mask[i]);
}
return 1;
default:
return 0;
}
}
static int is_link_query(unsigned long request) {
return request == SIOCGIFHWADDR || request == SIOCGIFFLAGS || request == SIOCGIFMTU
|| request == SIOCGIFINDEX || request == SIOCGIFADDR || request == SIOCGIFNETMASK
|| request == SIOCGIFBRDADDR;
}
void bl_kgsl_chip_id_fixup(unsigned long request, void *arg, int rc); /* kgslid.c */
int bl_kgsl_poll(int (*real)(int, unsigned long, void *), int fd, unsigned long request,
void *arg, int *rc) __attribute__((visibility("hidden")));
int bl_ntsync_ioctl(int fd, unsigned long request, void *arg, int *rc) __attribute__((visibility("hidden")));
int bl_drm_gem_close(int fd, unsigned long request, void *arg, int *rc) __attribute__((visibility("hidden")));
/* Every DRM and evdev call comes through here, so the lookup is done once. Two threads racing
* to store it store the same pointer. */
int ioctl(int fd, unsigned long request, ...) {
typedef int (*ioctl_fn)(int, unsigned long, void *);
static ioctl_fn real;
va_list ap;
va_start(ap, request);
void *arg = va_arg(ap, void *);
va_end(ap);
int rc;
if (bl_ntsync_ioctl(fd, request, arg, &rc)) return rc;
if (bl_drm_gem_close(fd, request, arg, &rc)) return rc;
if (real == NULL) real = (ioctl_fn) dlsym(RTLD_NEXT, "ioctl");
if (!bl_kgsl_poll(real, fd, request, arg, &rc)) rc = real(fd, request, arg);
bl_kgsl_chip_id_fixup(request, arg, rc);
if (arg == NULL || !is_link_query(request)) return rc;
int saved = errno;
if (answer_ifreq(request, (struct ifreq *) arg, rc)) return 0;
errno = saved;
return rc;
}
static void print_v6(FILE *out, const unsigned char *bytes) {
for (int i = 0; i < 16; i++) fprintf(out, "%02x", bytes[i]);
}
static unsigned v6_scope(const struct link_addr *addr) {
if (memcmp(addr, &LO_V6, sizeof(*addr)) == 0) return 0x10;
return is_link_local(addr) ? 0x20 : 0x00;
}
static void write_table(FILE *out, const char *table, const struct link *link) {
static const unsigned char zero[16];
unsigned char mask[16];
if (strcmp(table, "route") == 0) {
fprintf(out, "Iface\tDestination\tGateway \tFlags\tRefCnt\tUse\tMetric\tMask\t\tMTU\tWindow\tIRTT\n");
for (int i = 0; i < link->gateway_count; i++) {
if (link->gateways[i].family != AF_INET) continue;
unsigned gw;
memcpy(&gw, link->gateways[i].bytes, 4);
fprintf(out, "%s\t00000000\t%08X\t0003\t0\t0\t0\t00000000\t0\t0\t0\n", link->name, gw);
}
for (int i = 0; i < link->addr_count; i++) {
if (link->addrs[i].family != AF_INET) continue;
unsigned addr, net;
prefix_mask(AF_INET, link->addrs[i].prefix, mask);
memcpy(&addr, link->addrs[i].bytes, 4);
memcpy(&net, mask, 4);
fprintf(out, "%s\t%08X\t00000000\t0001\t0\t0\t0\t%08X\t0\t0\t0\n",
link->name, addr & net, net);
}
} else if (strcmp(table, "ipv6_route") == 0) {
for (int i = 0; i < link->gateway_count; i++) {
if (link->gateways[i].family != AF_INET6) continue;
print_v6(out, zero);
fprintf(out, " 00 ");
print_v6(out, zero);
fprintf(out, " 00 ");
print_v6(out, link->gateways[i].bytes);
fprintf(out, " 00000400 00000001 00000000 00000003 %8s\n", link->name);
}
for (int i = 0; i < link->addr_count; i++) {
if (link->addrs[i].family != AF_INET6) continue;
unsigned char net[16];
prefix_mask(AF_INET6, link->addrs[i].prefix, mask);
for (int b = 0; b < 16; b++) net[b] = link->addrs[i].bytes[b] & mask[b];
print_v6(out, net);
fprintf(out, " %02x ", link->addrs[i].prefix);
print_v6(out, zero);
fprintf(out, " 00 ");
print_v6(out, zero);
fprintf(out, " 00000100 00000001 00000000 00000001 %8s\n", link->name);
}
} else if (strcmp(table, "if_inet6") == 0) {
print_v6(out, LO_V6.bytes);
fprintf(out, " %02x %02x %02x 80 %8s\n", LO_INDEX, LO_V6.prefix, v6_scope(&LO_V6), LO_NAME);
for (int i = 0; i < link->addr_count; i++) {
if (link->addrs[i].family != AF_INET6) continue;
print_v6(out, link->addrs[i].bytes);
fprintf(out, " %02x %02x %02x 80 %8s\n", link->index, link->addrs[i].prefix,
v6_scope(&link->addrs[i]), link->name);
}
} else if (strcmp(table, "dev") == 0) {
fprintf(out, "Inter-| Receive | Transmit\n"
" face |bytes packets errs drop fifo frame compressed multicast|"
"bytes packets errs drop fifo colls carrier compressed\n");
fprintf(out, "%6s: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0\n", LO_NAME);
fprintf(out, "%6s: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0\n", link->name);
} else if (strcmp(table, "arp") == 0) {
fprintf(out, "IP address HW type Flags HW address Mask Device\n");
} else {
fprintf(out, "1\n");
}
}
static const char *denied_table(const char *path) {
static const char *const tables[] = { "route", "ipv6_route", "if_inet6", "dev", "arp" };
if (strncmp(path, "/proc/net/", 10) == 0) {
for (size_t i = 0; i < sizeof(tables) / sizeof(tables[0]); i++) {
if (strcmp(path + 10, tables[i]) == 0) return tables[i];
}
return NULL;
}
size_t len = strlen(path);
if (strncmp(path, "/sys/class/net/", 15) == 0 && len > 8 && strcmp(path + len - 8, "/carrier") == 0) {
return "carrier";
}
return NULL;
}
/* A memfd rather than fmemopen(): the stream owns its contents, so fclose() frees everything. */
static FILE *synthesize(const char *table) {
struct link link;
if (!load_link(&link)) return NULL;
int fd = memfd_create("droiddeck-net", MFD_CLOEXEC);
if (fd < 0) return NULL;
FILE *out = fdopen(fd, "w+");
if (out == NULL) {
close(fd);
return NULL;
}
write_table(out, table, &link);
if (fflush(out) != 0) {
fclose(out);
return NULL;
}
rewind(out);
return out;
}
/* tracer.c */
int bl_status_without_tracer(const char *path, int flags) __attribute__((visibility("hidden")));
static FILE *open_stream(const char *symbol, const char *path, const char *mode) {
typedef FILE *(*fopen_fn)(const char *, const char *);
int status = mode && mode[0] == 'r' && !strchr(mode, '+')
? bl_status_without_tracer(path, O_RDONLY | O_CLOEXEC) : -1;
if (status >= 0) {
FILE *copy = fdopen(status, "r");
if (copy == NULL) close(status);
return copy;
}
FILE *f = ((fopen_fn) dlsym(RTLD_NEXT, symbol))(path, mode);
if (f || path == NULL || mode == NULL || mode[0] != 'r') return f;
int saved = errno;
const char *table = denied_table(path);
if (table && (f = synthesize(table)) != NULL) return f;
errno = saved;
return NULL;
}
FILE *fopen(const char *path, const char *mode) {
return open_stream("fopen", path, mode);
}
FILE *fopen64(const char *path, const char *mode) {
return open_stream("fopen64", path, mode);
}
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