Systemd/src/shared/firewall-util.c

/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include <errno.h>
#include <stddef.h>
#include <string.h>

#include "alloc-util.h"
#include "firewall-util.h"
#include "firewall-util-private.h"

static enum FirewallBackend firewall_backend_probe(FirewallContext *ctx) {
        if (fw_nftables_init(ctx) == 0)
               return FW_BACKEND_NFTABLES;
#if HAVE_LIBIPTC
        return FW_BACKEND_IPTABLES;
#else
        return FW_BACKEND_NONE;
#endif
}

int fw_ctx_new(FirewallContext **ret) {
        _cleanup_free_ FirewallContext *ctx = NULL;

        ctx = new0(FirewallContext, 1);
        if (!ctx)
                return -ENOMEM;

        /* could probe here.  However, this means that we will load
         * iptable_nat or nf_tables, both will enable connection tracking.
         *
         * Alternative would be to probe here but only call
         * fw_ctx_new when nspawn/networkd know they will call
         * fw_add_masquerade/local_dnat later anyway.
         */
        *ret = TAKE_PTR(ctx);
        return 0;
}

FirewallContext *fw_ctx_free(FirewallContext *ctx) {
        if (!ctx)
                return NULL;

        if (ctx->firewall_backend == FW_BACKEND_NFTABLES)
                fw_nftables_exit(ctx);

        return mfree(ctx);
}

int fw_add_masquerade(
                FirewallContext **fw_ctx,
                bool add,
                int af,
                const union in_addr_union *source,
                unsigned source_prefixlen) {
        FirewallContext *ctx;
        int r;

        if (!*fw_ctx) {
                r = fw_ctx_new(fw_ctx);
                if (r < 0)
                        return r;
        }

        ctx = *fw_ctx;
        if (ctx->firewall_backend == FW_BACKEND_NONE)
                ctx->firewall_backend = firewall_backend_probe(ctx);

        switch (ctx->firewall_backend) {
        case FW_BACKEND_NONE:
                return -EOPNOTSUPP;
#if HAVE_LIBIPTC
        case FW_BACKEND_IPTABLES:
                return fw_iptables_add_masquerade(add, af, source, source_prefixlen);
#endif
        case FW_BACKEND_NFTABLES:
                return fw_nftables_add_masquerade(ctx, add, af, source, source_prefixlen);
        }

        return -EOPNOTSUPP;
}

int fw_add_local_dnat(
                FirewallContext **fw_ctx,
                bool add,
                int af,
                int protocol,
                uint16_t local_port,
                const union in_addr_union *remote,
                uint16_t remote_port,
                const union in_addr_union *previous_remote) {
        FirewallContext *ctx;

        if (!*fw_ctx) {
                int ret = fw_ctx_new(fw_ctx);
                if (ret < 0)
                        return ret;
        }

        ctx = *fw_ctx;
        if (ctx->firewall_backend == FW_BACKEND_NONE)
                ctx->firewall_backend = firewall_backend_probe(ctx);

        switch (ctx->firewall_backend) {
        case FW_BACKEND_NONE:
                return -EOPNOTSUPP;
        case FW_BACKEND_NFTABLES:
                return fw_nftables_add_local_dnat(ctx, add, af, protocol, local_port, remote, remote_port, previous_remote);
#if HAVE_LIBIPTC
        case FW_BACKEND_IPTABLES:
                return fw_iptables_add_local_dnat(add, af, protocol, local_port, remote, remote_port, previous_remote);
#endif
        }

        return -EOPNOTSUPP;
}