sslh/processes.c

/* 
  Processes that are common to sslh-ev and sslh-select
 
# Copyright (C) 2021-2025  Yves Rutschle
# 
# This program is free software; you can redistribute it
# and/or modify it under the terms of the GNU General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later
# version.
# 
# This program is distributed in the hope that it will be
# useful, but WITHOUT ANY WARRANTY; without even the implied
# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
# PURPOSE.  See the GNU General Public License for more
# details.
# 
# The full text for the General Public License is here:
# http://www.gnu.org/licenses/gpl.html

*/

#include "udp-listener.h"
#include "tcp-listener.h"
#include "processes.h"
#include "probe.h"
#include "log.h"

/* Struct to keep track of an association of a forked PID to its
 * listening socket and its protocol */
struct pid2proto {
    pid_t pid;
    struct listen_endpoint* endpoint;
    struct sslhcfg_protocols_item* proto;
};


int tidy_connection(struct connection *cnx, struct loop_info* fd_info)
{
    int i;

    for (i = 0; i < 2; i++) {
        if (cnx->q[i].fd != -1) {
            print_message(msg_fd, "closing fd %d\n", cnx->q[i].fd);

            watchers_del_read(fd_info->watchers, cnx->q[i].fd);
            watchers_del_write(fd_info->watchers, cnx->q[i].fd);
            close(cnx->q[i].fd);
        }
        if (cnx->q[i].begin_deferred_data)
            free(cnx->q[i].begin_deferred_data);
    }

    if (cnx->type == SOCK_DGRAM)
        udp_tidy(cnx, fd_info);

    if (gap_remove_ptr(fd_info->probing_list, cnx, fd_info->num_probing) != -1)
        fd_info->num_probing--;

    dec_proto_connections(cnx->proto);
    dec_listen_connections(cnx->endpoint);

    collection_remove_cnx(fd_info->collection, cnx);
    return 0;
}



/* Process a connection that is active in read */

void cnx_read_process(struct loop_info* fd_info, int fd)
{
    cnx_collection* collection = fd_info->collection;
    struct connection* cnx = collection_get_cnx_from_fd(collection, fd);
    switch (cnx->type)  {
    case SOCK_STREAM:
        tcp_read_process(fd_info, fd);
        break;

    case SOCK_DGRAM:
        udp_s2c_forward(cnx);
        break;

    default:
        print_message(msg_int_error, "cnx_read_process: Illegal connection type %d\n", cnx->type);
        dump_connection(cnx);
        exit(1);
    }
}


/* Process a connection that accepts a socket
 * (For UDP, this means all traffic coming from remote clients)
 * Returns new connection object, or NULL
 * */
struct connection* cnx_accept_process(struct loop_info* fd_info, struct listen_endpoint* listen_socket)
{
    int fd = listen_socket->socketfd;
    int type = listen_socket->type;
    struct connection* cnx;

    udp_timeouts(fd_info);

    switch (type) {
    case SOCK_STREAM:
        cnx = accept_new_connection(listen_socket, fd_info);
        if (!cnx) return NULL;

        break;

    case SOCK_DGRAM:
        cnx = udp_c2s_forward(fd, fd_info);
        if (!cnx) return NULL;
        break;

    default:
        print_message(msg_int_error, "Inconsistent cnx type: %d\n", type);
        exit(1);
    }

    int new_fd = cnx->q[0].fd;
    watchers_add_read(fd_info->watchers, new_fd);
    return cnx;
}



typedef struct pid2proto* hash_item;
#include "hash.h"

static int pid_make_key(hash_item item) 
{
    return item->pid;
}

static int pid_cmp(hash_item item1, hash_item item2)
{
    return item1->pid != item2->pid;
}

/* When a child has died, update the counts appropriately */
void decrease_forked_connection(struct loop_info* loop, pid_t pid) {
    struct pid2proto p2p = { .pid = pid };
    struct pid2proto* found = hash_find(loop->pid2proto, &p2p);
    if (!found) {
        print_message(msg_int_error, "SIGCHLD for unknown pid %d\n", pid);
        return;
    }
    dec_proto_connections(found->proto);
    dec_listen_connections(found->endpoint);

    hash_remove(loop->pid2proto, found);
    free(found);
}


typedef struct pid2proto* hash_item;
#include "hash.h"

int has_space_to_fork(struct loop_info* fd_info)
{
    return hash_insertable(fd_info->pid2proto);
}


void remember_child_data(struct loop_info* fd_info,
                         struct connection* cnx, pid_t pid)
{
    struct pid2proto* pid2proto = malloc(sizeof(*pid2proto));
    pid2proto->pid = pid;
    pid2proto->proto = cnx->proto;
    pid2proto->endpoint = cnx->endpoint;
    if (hash_insert(fd_info->pid2proto, pid2proto)) {
        print_message(msg_int_error, "hash_insert for pid %d failed\n", pid);
        /* This should not happen as called is supposed to check that space is
         * available in the hash */
        exit(1);
    }
}

static int max_forking_connections(void)
{
    int max_cnx = 0;
    for (int i = 0; i < cfg.protocols_len; i++) {
        if (cfg.protocols[i].fork) {
            if (cfg.protocols[i].max_connections_is_present)
                max_cnx += cfg.protocols[i].max_connections;
            else max_cnx += 512; /* A magic number that's hopefully high enough */
        }
    }
    return max_cnx;
}

static int next_power_of_two(int n)
{
    n |= (n >> 16);
    n |= (n >> 4);
    n |= (n >> 2);
    n |= (n >> 1);
    return n + 1;
}

void loop_init(struct loop_info* loop, struct listen_endpoint* listen_sockets, int num_addr_listen)
{
    memset(loop, 0, sizeof(*loop));
    loop->collection = collection_init(0);
    loop->probing_list = gap_init(0);
    CHECK_ALLOC(loop->probing_list, "gap_init");

    udp_init(loop);
    tcp_init();

    loop->listen_sockets = listen_sockets;
    loop->num_addr_listen = num_addr_listen;

    int max_forks = next_power_of_two(max_forking_connections());
    loop->pid2proto = hash_init(2 * max_forks, pid_make_key, pid_cmp);
    CHECK_ALLOC(loop->pid2proto, "hash_init");
}