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Fix tcp_ping for non-existent local network hosts
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Fixes #2042

We can't just assume select() exiting before the timeout to be a
success, since connect() can actually tell us there's no route to host
or other errors.
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mmuman committed Sep 24, 2024
1 parent 568d7e7 commit b05810d
Showing 1 changed file with 3 additions and 1 deletion.
4 changes: 3 additions & 1 deletion src/read_tcpip.cc
Original file line number Diff line number Diff line change
Expand Up @@ -133,10 +133,12 @@ void print_tcp_ping(struct text_object *obj, char *p, unsigned int p_max_size) {
if (errno == EINPROGRESS) { // but EINPROGRESS is only a "false fail"
gettimeofday(&tv1, nullptr);
if (select(sock + 1, nullptr, &writefds, nullptr, &timeout) != -1) {
int ret = 0;
socklen_t len = sizeof(ret);
gettimeofday(&tv2, nullptr);
usecdiff =
((tv2.tv_sec - tv1.tv_sec) * 1000000) + tv2.tv_usec - tv1.tv_usec;
if (usecdiff <= TCP_PING_TIMEOUT * 1000000) {
if (getsockopt(sock, SOL_SOCKET, SO_ERROR, &ret, &len) == 0 && ret == 0) {
snprintf(p, p_max_size, "%llu", (usecdiff / 1000U));
} else {
#define TCP_PING_FAILED "down"
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