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[Pick][0.8 to main] | fix potential race condition in DefaultResolver when discard_cache() #710

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merged 1 commit into from
Feb 7, 2025
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[Pick][0.8 to main] | fix potential race condition in DefaultResolver when discard_cache() #710

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15 changes: 5 additions & 10 deletions net/utils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -263,8 +263,9 @@ class DefaultResolver : public Resolver {
IPAddr addr;
IPAddrNode(IPAddr addr) : addr(addr) {}
};
using IPAddrList = intrusive_list<IPAddrNode>;

struct IPAddrList : public intrusive_list<IPAddrNode>, rwlock {
~IPAddrList() { delete_all(); }
};
IPAddr do_resolve(std::string_view host, Delegate<bool, IPAddr> filter) {
auto ctr = [&]() -> IPAddrList* {
auto addrs = new IPAddrList();
Expand Down Expand Up @@ -295,6 +296,7 @@ class DefaultResolver : public Resolver {
};
auto ips = dnscache_.borrow(host, ctr);
if (ips->empty()) LOG_ERRNO_RETURN(0, IPAddr(), "Domain resolution for '`' failed", host);
scoped_rwlock _(*ips, RLOCK);
auto ret = ips->front();
ips->node = ret->next(); // access in round robin order
return ret->addr;
Expand All @@ -303,13 +305,6 @@ class DefaultResolver : public Resolver {
public:
DefaultResolver(uint64_t cache_ttl, uint64_t resolve_timeout)
: dnscache_(cache_ttl), resolve_timeout_(resolve_timeout) {}
~DefaultResolver() {
for (auto it : dnscache_) {
((IPAddrList*)it->_obj)->delete_all();
}
dnscache_.clear();
}

IPAddr resolve(std::string_view host) override {
return do_resolve(host, nullptr);
}
Expand All @@ -321,9 +316,9 @@ class DefaultResolver : public Resolver {
void discard_cache(std::string_view host, IPAddr ip) override {
auto ipaddr = dnscache_.borrow(host);
if (ip.undefined() || ipaddr->empty()) {
ipaddr->delete_all();
ipaddr.recycle(true);
} else {
scoped_rwlock _(*ipaddr, WLOCK);
for (auto itr = ipaddr->rbegin(); itr != ipaddr->rend(); itr++) {
if ((*itr)->addr == ip) {
ipaddr->erase(*itr);
Expand Down
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