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android: define getifaddrs/freeifaddrs for the api-21 sysroot

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Turning on hbb_common's "webrtc" feature pulls webrtc-util into the android
link, and its ifaces() -- reached from vnet::Net::new() on every ICE gather --
calls getifaddrs(). bionic exports getifaddrs/freeifaddrs only from API 24,
while flutter/ndk_*.sh builds against --platform 21, so every abi failed to
link on the undefined symbols.

Raising the platform to 24 would have to drag minSdkVersion 22 with it and
turn the link error into a load-time one on Android 5.1/6.0, so define the
two symbols instead, using the RTM_GETLINK + RTM_GETADDR netlink dump bionic
itself uses. The definition also shadows bionic's on API >= 24 rather than
delegating to it, so the path that ships is the path every test device runs.

Checked against synthesised netlink dumps on the host -- link/address parsing,
prefix masks, point-to-point, ipv6 scope ids, malformed and truncated messages
-- under UBSan and byte-exact guard malloc, with a deliberately unsigned
remainder as the negative control.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
rustdesk
2026-08-07 17:17:22 +08:00
parent 3f5ce9acae
commit 704f7495b9
2 changed files with 416 additions and 0 deletions
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12
build.rs
View File

@@ -43,6 +43,15 @@ fn build_manifest() {
}
}
// bionic only exports getifaddrs()/freeifaddrs() from API 24, while the jniLibs
// are built against the API 21 sysroot (flutter/ndk_*.sh). webrtc-util calls
// them, so without this the android link fails on undefined symbols.
fn build_android_ifaddrs() {
let file = "src/platform/android_ifaddrs.c";
cc::Build::new().file(file).compile("android_ifaddrs");
println!("cargo:rerun-if-changed={}", file);
}
fn install_android_deps() {
let target_os = std::env::var("CARGO_CFG_TARGET_OS").unwrap();
if target_os != "android" {
@@ -89,5 +98,8 @@ fn main() {
build_mac();
println!("cargo:rustc-link-lib=framework=ApplicationServices");
}
if target_os == "android" {
build_android_ifaddrs();
}
println!("cargo:rerun-if-changed=build.rs");
}

404
src/platform/android_ifaddrs.c Normal file
View File

@@ -0,0 +1,404 @@
/*
* getifaddrs()/freeifaddrs() for Android: bionic only exports them from API 24,
* while the jniLibs are built against the API 21 sysroot (flutter/ndk_*.sh) and
* webrtc-util calls them whenever WebRTC gathers ICE candidates.
*
* Only AF_INET and AF_INET6 entries are reported; the AF_PACKET ones the real
* getifaddrs() also returns have no reader in this build.
*/
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ifaddrs.h>
#include <net/if.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
/* Refuse a single netlink datagram larger than this rather than grow forever. */
#define RD_NL_MAX_BUF (1024 * 1024)
/* A dump that never terminates must not hang the caller. */
#define RD_NL_MAX_DATAGRAMS 4096
typedef int (*rd_nl_cb)(struct nlmsghdr *nlh, void *ctx);
struct rd_link_info {
unsigned int index;
unsigned int flags;
char name[IFNAMSIZ + 1];
};
struct rd_link_table {
struct rd_link_info *items;
size_t len;
size_t cap;
};
/* One allocation per reported address; `ifa` first so freeifaddrs() can free
* the node it is handed. */
struct rd_ifaddrs_storage {
struct ifaddrs ifa;
struct sockaddr_storage addr;
struct sockaddr_storage netmask;
struct sockaddr_storage ifu;
char name[IFNAMSIZ + 1];
};
struct rd_addr_ctx {
const struct rd_link_table *links;
struct ifaddrs *head;
struct ifaddrs *tail;
};
static void rd_parse_rtattr(struct rtattr *rta, int len, struct rtattr **tb, int max)
{
memset(tb, 0, sizeof(*tb) * ((size_t)max + 1));
for (; RTA_OK(rta, len); rta = RTA_NEXT(rta, len)) {
if (rta->rta_type <= (unsigned short)max && tb[rta->rta_type] == NULL)
tb[rta->rta_type] = rta;
}
}
/* `len` must stay signed: NLMSG_NEXT subtracts the *aligned* length, which
* overshoots on an unaligned trailing message, and only a negative remainder
* stops NLMSG_OK from reading past the buffer. */
static int rd_nl_parse(char *buf, int len, unsigned short reply_type, unsigned int seq,
rd_nl_cb cb, void *ctx, int *done)
{
struct nlmsghdr *nlh = (struct nlmsghdr *)buf;
for (; NLMSG_OK(nlh, len); nlh = NLMSG_NEXT(nlh, len)) {
if (nlh->nlmsg_seq != seq)
continue;
if (nlh->nlmsg_type == NLMSG_DONE) {
*done = 1;
return 0;
}
if (nlh->nlmsg_type == NLMSG_ERROR) {
struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(nlh);
if (nlh->nlmsg_len >= NLMSG_LENGTH(sizeof(*err)) && err->error != 0)
errno = -err->error;
else
errno = EIO;
return -1;
}
if (nlh->nlmsg_type != reply_type)
continue;
if (cb(nlh, ctx) != 0)
return -1;
/* A non-multipart reply is the whole answer; nothing follows it. */
if ((nlh->nlmsg_flags & NLM_F_MULTI) == 0) {
*done = 1;
return 0;
}
}
return 0;
}
static int rd_nl_dump(int fd, unsigned short request_type, unsigned short reply_type,
unsigned int seq, rd_nl_cb cb, void *ctx)
{
struct {
struct nlmsghdr nlh;
struct rtgenmsg gen;
} req;
struct sockaddr_nl kernel;
char *buf;
size_t cap = 8192;
int datagrams = 0;
int done = 0;
int rc = -1;
int saved;
memset(&req, 0, sizeof(req));
req.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(req.gen));
req.nlh.nlmsg_type = request_type;
req.nlh.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
req.nlh.nlmsg_seq = seq;
req.gen.rtgen_family = AF_UNSPEC;
memset(&kernel, 0, sizeof(kernel));
kernel.nl_family = AF_NETLINK;
for (;;) {
if (sendto(fd, &req, req.nlh.nlmsg_len, 0, (struct sockaddr *)&kernel,
sizeof(kernel)) >= 0)
break;
if (errno != EINTR)
return -1;
}
buf = (char *)malloc(cap);
if (buf == NULL) {
errno = ENOMEM;
return -1;
}
while (!done) {
/* MSG_PEEK|MSG_TRUNC reports the datagram's real size, so an
* undersized buffer costs a resize instead of a silent truncation. */
ssize_t n = recv(fd, buf, cap, MSG_PEEK | MSG_TRUNC);
if (n < 0) {
if (errno == EINTR)
continue;
goto out;
}
if ((size_t)n > cap) {
char *grown;
if ((size_t)n > RD_NL_MAX_BUF) {
errno = EMSGSIZE;
goto out;
}
grown = (char *)realloc(buf, (size_t)n);
if (grown == NULL) {
errno = ENOMEM;
goto out;
}
buf = grown;
cap = (size_t)n;
continue;
}
n = recv(fd, buf, cap, 0);
if (n < 0) {
if (errno == EINTR)
continue;
goto out;
}
if (n == 0 || ++datagrams > RD_NL_MAX_DATAGRAMS) {
errno = EIO;
goto out;
}
if (rd_nl_parse(buf, (int)n, reply_type, seq, cb, ctx, &done) != 0)
goto out;
}
rc = 0;
out:
saved = errno;
free(buf);
errno = saved;
return rc;
}
static int rd_link_cb(struct nlmsghdr *nlh, void *ctx)
{
struct rd_link_table *t = (struct rd_link_table *)ctx;
struct ifinfomsg *ifi;
struct rtattr *tb[IFLA_IFNAME + 1];
struct rd_link_info *slot;
int payload;
int namelen;
if (nlh->nlmsg_len < NLMSG_LENGTH(sizeof(*ifi)))
return 0;
ifi = (struct ifinfomsg *)NLMSG_DATA(nlh);
payload = (int)nlh->nlmsg_len - (int)NLMSG_SPACE(sizeof(*ifi));
if (payload < 0)
payload = 0;
rd_parse_rtattr(IFLA_RTA(ifi), payload, tb, IFLA_IFNAME);
/* An interface we cannot name is of no use: callers dereference ifa_name. */
if (tb[IFLA_IFNAME] == NULL || (int)RTA_PAYLOAD(tb[IFLA_IFNAME]) <= 0)
return 0;
if (t->len == t->cap) {
size_t ncap = t->cap ? t->cap * 2 : 16;
struct rd_link_info *items =
(struct rd_link_info *)realloc(t->items, ncap * sizeof(*items));
if (items == NULL) {
errno = ENOMEM;
return -1;
}
t->items = items;
t->cap = ncap;
}
slot = &t->items[t->len];
memset(slot, 0, sizeof(*slot));
slot->index = (unsigned int)ifi->ifi_index;
slot->flags = ifi->ifi_flags;
namelen = (int)RTA_PAYLOAD(tb[IFLA_IFNAME]);
if (namelen > IFNAMSIZ)
namelen = IFNAMSIZ;
memcpy(slot->name, RTA_DATA(tb[IFLA_IFNAME]), (size_t)namelen);
slot->name[namelen] = '\0';
t->len++;
return 0;
}
static const struct rd_link_info *rd_link_find(const struct rd_link_table *t,
unsigned int index)
{
size_t i;
for (i = 0; i < t->len; i++) {
if (t->items[i].index == index)
return &t->items[i];
}
return NULL;
}
static void rd_fill_mask(unsigned char *out, int len, unsigned int prefix)
{
int i;
if (prefix > (unsigned int)len * 8)
prefix = (unsigned int)len * 8;
for (i = 0; i < len; i++) {
if (prefix >= 8) {
out[i] = 0xff;
prefix -= 8;
} else if (prefix > 0) {
out[i] = (unsigned char)(0xff << (8 - prefix));
prefix = 0;
} else {
out[i] = 0;
}
}
}
static void rd_set_in(struct sockaddr_storage *ss, const void *addr)
{
struct sockaddr_in *sin = (struct sockaddr_in *)ss;
sin->sin_family = AF_INET;
memcpy(&sin->sin_addr, addr, 4);
}
static int rd_addr_cb(struct nlmsghdr *nlh, void *ctx)
{
struct rd_addr_ctx *c = (struct rd_addr_ctx *)ctx;
struct ifaddrmsg *ifa;
struct rtattr *tb[IFA_BROADCAST + 1];
struct rtattr *ra;
const struct rd_link_info *link;
struct rd_ifaddrs_storage *st;
int payload;
if (nlh->nlmsg_len < NLMSG_LENGTH(sizeof(*ifa)))
return 0;
ifa = (struct ifaddrmsg *)NLMSG_DATA(nlh);
if (ifa->ifa_family != AF_INET && ifa->ifa_family != AF_INET6)
return 0;
/* Without the link entry there is no name, and callers deref ifa_name. */
link = rd_link_find(c->links, ifa->ifa_index);
if (link == NULL)
return 0;
payload = (int)nlh->nlmsg_len - (int)NLMSG_SPACE(sizeof(*ifa));
if (payload < 0)
payload = 0;
rd_parse_rtattr(IFA_RTA(ifa), payload, tb, IFA_BROADCAST);
/* On a point-to-point link IFA_ADDRESS holds the peer and IFA_LOCAL the
* local address; ipv6 only ever sets IFA_ADDRESS. */
if (ifa->ifa_family == AF_INET)
ra = tb[IFA_LOCAL] ? tb[IFA_LOCAL] : tb[IFA_ADDRESS];
else
ra = tb[IFA_ADDRESS] ? tb[IFA_ADDRESS] : tb[IFA_LOCAL];
if (ra == NULL)
return 0;
if ((int)RTA_PAYLOAD(ra) < (ifa->ifa_family == AF_INET ? 4 : 16))
return 0;
st = (struct rd_ifaddrs_storage *)calloc(1, sizeof(*st));
if (st == NULL) {
errno = ENOMEM;
return -1;
}
memcpy(st->name, link->name, sizeof(st->name));
st->ifa.ifa_name = st->name;
st->ifa.ifa_flags = link->flags;
st->ifa.ifa_addr = (struct sockaddr *)&st->addr;
st->ifa.ifa_netmask = (struct sockaddr *)&st->netmask;
if (ifa->ifa_family == AF_INET) {
struct sockaddr_in *mask = (struct sockaddr_in *)&st->netmask;
rd_set_in(&st->addr, RTA_DATA(ra));
mask->sin_family = AF_INET;
rd_fill_mask((unsigned char *)&mask->sin_addr, 4, ifa->ifa_prefixlen);
if ((link->flags & IFF_POINTOPOINT) && tb[IFA_ADDRESS] && tb[IFA_LOCAL] &&
(int)RTA_PAYLOAD(tb[IFA_ADDRESS]) >= 4 &&
memcmp(RTA_DATA(tb[IFA_ADDRESS]), RTA_DATA(tb[IFA_LOCAL]), 4) != 0) {
rd_set_in(&st->ifu, RTA_DATA(tb[IFA_ADDRESS]));
st->ifa.ifa_dstaddr = (struct sockaddr *)&st->ifu;
} else if (tb[IFA_BROADCAST] && (int)RTA_PAYLOAD(tb[IFA_BROADCAST]) >= 4) {
rd_set_in(&st->ifu, RTA_DATA(tb[IFA_BROADCAST]));
st->ifa.ifa_broadaddr = (struct sockaddr *)&st->ifu;
}
} else {
struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&st->addr;
struct sockaddr_in6 *mask = (struct sockaddr_in6 *)&st->netmask;
sin6->sin6_family = AF_INET6;
memcpy(&sin6->sin6_addr, RTA_DATA(ra), 16);
/* A link-local address is not routable without its scope id. */
if (IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr) ||
IN6_IS_ADDR_MC_LINKLOCAL(&sin6->sin6_addr))
sin6->sin6_scope_id = ifa->ifa_index;
mask->sin6_family = AF_INET6;
rd_fill_mask((unsigned char *)&mask->sin6_addr, 16, ifa->ifa_prefixlen);
}
if (c->tail != NULL)
c->tail->ifa_next = &st->ifa;
else
c->head = &st->ifa;
c->tail = &st->ifa;
return 0;
}
void freeifaddrs(struct ifaddrs *ifa)
{
while (ifa != NULL) {
struct ifaddrs *next = ifa->ifa_next;
free(ifa);
ifa = next;
}
}
int getifaddrs(struct ifaddrs **ifap)
{
struct rd_link_table links;
struct rd_addr_ctx ctx;
int fd;
int saved;
if (ifap == NULL) {
errno = EINVAL;
return -1;
}
*ifap = NULL;
memset(&links, 0, sizeof(links));
memset(&ctx, 0, sizeof(ctx));
ctx.links = &links;
fd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
if (fd < 0)
return -1;
if (rd_nl_dump(fd, RTM_GETLINK, RTM_NEWLINK, 1, rd_link_cb, &links) != 0)
goto fail;
if (rd_nl_dump(fd, RTM_GETADDR, RTM_NEWADDR, 2, rd_addr_cb, &ctx) != 0)
goto fail;
close(fd);
free(links.items);
*ifap = ctx.head;
return 0;
fail:
saved = errno;
close(fd);
free(links.items);
freeifaddrs(ctx.head);
errno = saved;
return -1;
}